Unit- X - Common communicable Disease

 Unit- X

Common communicable Disease

          Meaning , common communicable Diseases –Malaria, Typhoid, Cholera, Diarrhea, small pox, Whooping cough, Aids symptoms, cause and prevention.

Malaria 

Malaria is a mosquito-borne infectious disease of humans and other animals caused byeukaryotic protists (a type of microorganism) of the genus Plasmodium. The protists first infect the liver, then act as parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases progressing to coma or death. The disease is widespread in tropical and subtropical regions in a broad band around the equator, including much of Sub-Saharan Africa, Asia, and the Americas.

Five species of Plasmodium can infect and be transmitted by humans. Severe disease is largely caused by P. falciparum while the disease caused by P. vivax, P. ovale, andP. malariae is generally a milder form that is rarely fatal. The zoonotic speciesP. knowlesi, prevalent in Southeast Asia, causes malaria in macaques but can also cause severe infections in humans. Malaria is prevalent in tropical regions because of the significant amounts of rainfall, consistently high temperatures and high humidity, along with stagnant waters in which mosquito larvae readily mature, provide them with the environment they need for continuous breeding. Disease transmission can be reduced by preventing mosquito bites by distribution of mosquito nets and insect repellents, or with mosquito-control measures such as spraying insecticides and draining standing water.

The WHO has estimated that malaria annually causes over 200 million cases of fever;^[1]in 2010, around 655,000 people died from the disease, most of whom were children under the age of five.^[2] The actual number of deaths may be significantly higher, as precise statistics are unavailable in many rural areas, and many cases are undocumented.P. falciparum—responsible for the most severe form of malaria—causes the vast majority of deaths associated with the disease. Malaria is commonly associated with poverty, and can indeed be a cause of poverty and a major hindrance to economic development.

Despite a clear need, no vaccine offering a high level of protection currently exists. Efforts to develop one are ongoing. Several medications are available to prevent malaria in travelers to malaria-endemic countries (prophylaxis). A variety of antimalarial medicationsare available. Severe malaria is treated with intravenous or intramuscular quinine or, since the mid-2000s, the artemisinin derivative artesunate, which is superior to quinine in both children and adults. Resistance has developed to several antimalarial drugs, most notably chloroquine and artemisinin.

Typhoid fever

Signs and symptoms

Classically, the course of untreated typhoid fever is divided into 4 individual stages, each lasting approximately 1 week. In the 1st week, the temperature rises slowly with relative bradycardia, malaise, headache, and cough. A bloody nose (epistaxis) is seen in a quarter of cases and abdominal pain is also possible. There is leukopenia, a decrease in the number of circulating white blood cells, with eosinopenia and relative lymphocytosis, a positive reaction and blood cultures are positive for Salmonella typhi or paratyphi. The classic Widal test is negative in the first week.

In the second week of the infection, the patient lies prostrate with high fever in plateau around 40 °C (104 °F) and bradycardia(sphygmothermic dissociation), classically with a dicrotic pulse wave. Delirium is frequent, frequently calm, but sometimes agitated. This delirium gives to typhoid the nickname of "nervous fever". Rose spots appear on the lower chest and abdomen in around a third of patients. There are rhonchi in lung bases. The abdomen is distended and painful in the right lower quadrant where borborygmi can be heard. Diarrhea can occur in this stage: six to eight stools in a day, green with a characteristic smell, comparable to pea soup. However, constipation is also frequent. The spleen and liver are enlarged (hepatosplenomegaly) and tender, and there is elevation of liver transaminases. The Widal reaction is strongly positive with antiO and antiH antibodies. Blood cultures are sometimes still positive at this stage. (The major symptom of this fever is that the fever usually rises in the afternoon up to the first and second week.)

In the third week of typhoid fever, a number of complications can occur:

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       Smoll Fox

Smallpox was an infectious disease unique to humans, caused by either of two virusvariants, Variola major and Variola minor.^[1] The disease is also known by the Latinnames Variola or Variola vera, which is a derivative of the Latin varius, meaning "spotted", or varus, meaning "pimple". The term "smallpox" was first used in Britain in the 15th century to distinguish variola from the "great pox" (syphilis).^[2] The last naturally occurring case of smallpox (Variola minor) was diagnosed on 26 October 1977.^[3]

Smallpox localizes in small blood vessels of the skin and in the mouth and throat. In the skin it results in a characteristic maculopapular rash and, later, raised fluid-filled blisters.V. major produces a more serious disease and has an overall mortality rate of 30–35%.V. minor causes a milder form of disease (also known as alastrim, cottonpox,milkpox, whitepox, and Cuban itch) which kills about 1% of its victims.^[4][5] Long-term complications of V. major infection include characteristic scars, commonly on the face, which occur in 65–85% of survivors.^[6] Blindness resulting from corneal ulceration and scarring, and limb deformities due to arthritis and osteomyelitis are less common complications, seen in about 2–5% of cases.

Smallpox is believed to have emerged in human populations about 10,000 BC.^[2] The earliest physical evidence of it is probably the pustular rash on the mummified body of Pharaoh Ramses V of Egypt.^[7] The disease killed an estimated 400,000 Europeans annually during the closing years of the 18th century (including five reigning monarchs),^[8]and was responsible for a third of all blindness.^[4][9] Of all those infected, 20–60%—and over 80% of infected children—died from the disease.^[10] Smallpox was responsible for an estimated 300–500 million deaths during the 20th century.^[11][12][13] As recently as 1967, the World Health Organization (WHO) estimated that 15 million people contracted the disease and that two million died in that year.^[3]

After vaccination campaigns throughout the 19th and 20th centuries, the WHO certified the eradication of smallpox in 1979.^[3] Smallpox is one of two infectious diseases to have been eradicated, the other being rinderpest, which was declared eradicated in 

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AIDS

Signs and symptoms

Main article: Signs and symptom of HIV/AIDS

The three stages of HIV infection are: acute infection (also known as primary infection), latency and AIDS.^[11] Acute infection typically lasts for several weeks and may include symptoms such as a fever, swollen lymph nodes), inflammation of the throat, a rash, muscle pains, fatigue, and mouth and esophageal sores. The latency stage involves few or no symptoms and can last anywhere from two weeks to twenty years or more, depending on the individual. AIDS, the final stage of HIV infection, is defined by a low CD4+ T cell counts (fewer than 200 per ul), various opportunistic infections (such as Pneumocystis pneumonia (PCP) or toxoplasmosis of the brain), cancers (such as Kaposi’s sarcoma) and other conditions.^[12]

Acute infection

Main symptoms of acute HIV infection

The initial period following contracting HIV is called an acute or primary HIV infection.^[13] Many individuals develop an influenza-like illness or a mononucleosis-like illness 2–4 weeks post-exposure while others have no significant symptoms.^[14][15]Symptoms occur in 40-90% of cases and most commonly include: fever, large tender lymph nodes, throat inflammation, rash, headache, and sores of the mouth and genitals.^[13][15] The rash is classically maculopapular and on the trunk, occurring in 20-50% of cases.^[12] Some people also develop opportunistic infections at this point in time.^[13] Other symptoms may include include: nausea, vomiting, diarrhea, and neurological problems such as peripheral neuropathy and Guillain-Barre syndrome.^[15]The duration of symptoms varies, but is usually one or two weeks.^[15]

Because of the nonspecific nature of these symptoms, they are often not recognized as signs of HIV infection. Even if people go to their doctors or a hospital, they will often be misdiagnosed as having one of the more common infectious diseases with the same symptoms. Thus it is recommended that HIV be considered in those with an unexplained fever and risk factors for the disease.^[15]

Latency

A strong immune defense reduces the number of viral particles in the blood stream, marking the start of secondary or chronic HIV infection. The secondary stage of HIV infection can vary between two weeks and 20 years. During this phase of infection, HIV is active within lymph nodes, which typically become persistently swollen, in response to large amounts of virus that become trapped in the follicular dendritic cells (FDC) network.^[16] The surrounding tissues that are rich in CD4⁺ T cells may also become infected, and viral particles accumulate both in infected cells and as free virus. Individuals who are in this phase are still infectious. During this time,CD4⁺ CD45RO⁺ T cells carry most of the proviral load.^[17]

A small percentage (~5%) of HIV-1 infected individuals retain high levels of CD4+ T-cells without antiretroviral therapy for more than 5 years.^[18][15] However, most have detectable viral load and will eventually progress to AIDS without treatment.^[18] These individuals are classified as HIV controllers or long-term nonprogressors (LTNP).^[18] People who maintain CD4+ T cell counts and also have low or clinically undetectable viral load without anti-retroviral treatment are known as elite controllers or elite suppressors.^[18]

AIDS

Main symptoms of AIDS.

AIDS is defined as either a CD4⁺ T cell numbers below 200 cells per µL or is based on the occurrence of specific diseases in association with an HIV infection.^[15] Around half of people infected with HIV will develop AIDS within ten years if not treated.^[15] The most common initial conditions that alert to the presence of AIDS are PCP pneumonia (40%), HIV wasting syndrome (20%) and esophageal candidiasis.^[15] Other common symptoms include recurring respiratory tract infections (such as pneumonia,^[15],sinusitis, bronchitis, otitis media, pharyngitis), prostatitis, skin rashes, and oral ulcerations.

Opportunistic infections may be caused by bacteria, viruses, fungi and parasites that are normally controlled by the immune system.^[19] Which infections occur partly depends on what organism are common in the persons environment.^[15] These infections can affect nearly every organ system. The specific opportunistic infections which develops depend in part on the prevalence of these infections in the geographic area in which the patient lives.

People with AIDS have an increased risk of developing various viral induced cancers including: Kaposi's sarcoma, Burkitt’s lymphoma, primary central nervous system lymphoma, and cervical cancer.^[12] Kaposi's sarcoma is the most common cancer occurring in 10-20% of people with HIV.^[20] The second most common cancer is lymphoma which is the cause of death of nearly 16% of people with AIDS and is the initial sign of AIDS in 3-4%.^[20] Both these cancers are associated with human herpesvirus 8.^[20] Cervical cancer occurs more frequently in those with AIDS due to its association with human papillomavirus (HPV).^[20]

Additionally, they frequently have systemic symptoms like a prolonged fevers, sweats (particularly at night), swollen glands, chills, weakness, and weight loss.^[21][22] Diarrhea is another common symptoms present in ~90% of people with AIDS.^[23]

Transmission

Average per act risk of getting HIV by exposure route to an infected source
Exposure Route	Chance of infection
Blood Transfusion	90% [24]
Childbirth (to child)	25%[25]
Needle-sharing injection drug use	0.67%[24]
Percutaneous needle stick	0.30%[26]
Receptive anal intercourse*	0.04–3.0%[27]
Insertive anal intercourse*	0.06–0.056%[27]
Receptive penile-vaginal intercourse*	0.05–0.30%[27][28]
Insertive penile-vaginal intercourse*	0.01–0.38% [27][28]
Receptive oral intercourse*§	0–0.04% [27]
Insertive oral intercourse*§	0-0.005%[29]
* assuming no condom use § source refers to oral intercourse performed on a man

HIV is transmitted by three main routes: sexual contact, exposure to infected body fluids or tissues, and from mother to child during pregnancy, delivery, or breastfeeding (known as vertical transmission).^[2] There is no risk of acquiring HIV if exposed to feces, nasal secretions, saliva, sputum, sweat, tears, urine, or vomit unless these are contaminated with blood.^[26] It is possible to be infected by more than one strain of HIV, which is known as HIV superinfection orcoinfection.^[30]

Sexual

The majority of HIV infections are acquired through unprotected sexual relations where one partner has HIV.^[2] Worldwide, sexual contact between members of the opposite sex rather than between members of the same sex, result in most cases of transmission.^[2] In the United States, as of 2009, most sexual transmission occurred inmen who have sex with men^[2] with this population account for 64% of all new cases.^[31]

In high-income countries, the risk of female-to-male transmission is ~0.04% per act and male-to-female transmission is ~0.08% per act.^[32] For various reasons, these rates are four to ten times higher in low-income countries with rates of female-to-male transmission is ~0.38% per act and male-to-female transmission is ~0.30% per act.^[32] The risk from anal intercourse is ~1.7% per act^[32] and while the risk of transmission from oral sex is less it is still present.^[33] Per act risk is estimated at 0-0.04% for receptive oral intercourse.^[34]Case reports have documented the acquisition of HIV from receiving oral sex.^[35]

Risk increases in the presence of many sexually transmitted infections^[36] and genital ulcers.^[32] Genital ulcers increase the risk approximately fivefold^[32] and there is a lesser increase in risk from STIs such as gonorrhea, chlamydia, trichomoniasis, and bacterial vaginosis.^[34] Rough sex also appears to increase the risk.^[37]

The viral load of an infected person is important both in heterosexual and vertical transmission.^[38] During the first 2.5 month of an HIV infection a persons infectiousness is twelvefold higher due to this high viral load.^[34] Where the person is in the late stages of infection rates of transmission are approximately eightfold greater.^[32]

Commercial sex exposure impact risk with rates of female-to-male transmission of ~2.4% per act and male-to-female transmission is ~0.08% per act.^[32] Sexual assault is believed to have an increased risk of HIV transmission as condoms are rarely employed, physical trauma to the vagina or rectum may occurs, and there may be a greater risk of concurrent sexually transmitted infections.^[39]The percentage of those who are HIV positive and in jail for sexual assault in the United States is roughly 1%.^[40]

Body fluids

CDC poster from 1989 highlighting the threat of AIDS associated with drug use

The second most frequent mode of HIV transmission is via blood and blood products.^[2]Though it is not possible for mosquitoes or other insects to transmit HIV.^[2][41]

The risk from sharing a needle during drug injection is between 0.63 to 2.4% (ave. 0.8%).^[42] The risk of acquiring HIV from a needle stick from an HIV-infected person is about 0.3% (~1 in 333) and the risk following mucus membrane exposure to infected blood is 0.09% (~1:1000).^[26] In the United States intravenous drug user made up 12% of all new cases of HIV in 2009^[31] and in some areas more than 80% of people who inject drugs are HIV positive.^[2]

Blood transfusions with infected blood result in transmission of infection ~93% of the time.^[42] In developed countries the risk of acquiring HIV from a blood transfusion is extremely low (less than one in half a million) where improved donor selection and HIV screening is performed.^[2] In the UK the risk is reported at one in five million.^[43] However, in low income countries only half of the blood used for transfusions may be appropriately screened (as of 2008).^[44] It is estimated that up to 15% of HIV infections come from transfusion of infected blood and blood products in these areas (5% and 10% of global infections).^[2][45]

The reuse of syringes plays a significant role in HIV spread in sub-Saharan Africa with between 12 to 17% of cases in this region attributed to the practice as of 2009.^[46] The risk from a single unsafe injection is estimated at ~1.2%.^[46] Significant risks are also associated with invasive procedures, assisted delivery, and dental care in this area of the world.^[46] People giving or receiving tattoos,piercings, and scarification are theoretically at risk of infection but no confirmed cases have been documented.^[47]

Mother-to-child

HIV can be transmitted from mother to child during pregnancy, during delivery, and after delivery via breastfeeding.^[48] It is the third most common way HIV is transmitted globally.^[2] In the absence of treatment, the risk of transmission before or during birth is around 20% and in those who also breastfeed 35%.^[48] As of 2008, vertical transmission is the route of infection in 90% of children.^[48] With appropriate treatment this risk can be reduced to ~1%.^[48] This involves the mother taking antiretroviral during pregnancy and delivery, an elective caesarean section, and not breastfeeding, as well as the infant taking antiretrovirals after birth.^[49] Many of these measures are however not available in the developing world^[49] If blood contaminates food during pre-chewing it may pose a risk of transmission.^[47]

Virology

Main article: HIV virus

A diagram of the HIV virus

HIV/AIDS is a spectrum of disease causes by the HIV virus with AIDS being the ultimate clinical consequence of this infection. HIV is a retrovirus that primarily infects vital organs of the human immune system such as CD4⁺ T cells (a subset of T cells), macrophages anddendritic cells. It directly and indirectly destroys CD4⁺ T cells.^[50]

Once the number of CD4⁺ T cells per microliter (µL) of blood drops below 200, cellular immunity is lost. Acute HIV infection usually progresses over time to clinical latent HIV infection and then to early symptomatic HIV infection and later to AIDS, which is identified either on the basis of the amount of CD4⁺ T cells remaining in the blood, and/or the presence of certain infections, as noted above.^[51]

In the absence of antiretroviral therapy, the median time of progression from HIV infection to AIDS is nine to ten years, and the median survival time after developing AIDS is only 9.2 months.^[52] However, the rate of clinical disease progression varies widely between individuals, from two weeks up to 20 years.

Many factors affect the rate of progression. These include factors that influence the body's ability to defend against HIV such as the infected person's general immune function.^[53][54] Older people have weaker immune systems, and therefore have a greater risk of rapid disease progression than younger people.

Poor access to health care and the existence of coexisting infections such as tuberculosis also may predispose people to faster disease progression.^[52][55] The infected person's genetic inheritance plays an important role and some people are resistant to certain strains of HIV. An example of this is people with the homozygous CCR5-Δ32 variation are resistant to infection with certain strains of HIV.^[56] HIV is genetically variable and exists as different strains, which cause different rates of clinical disease progression.^[57][58][59]

Pathophysiology

Scanning electron micrograph of HIV-1, colored green, budding from a culturedlymphocyte.

After the virus enters the body there is a period of rapid viral replication, leading to an abundance of virus in the peripheral blood. During primary infection, the level of HIV may reach several million virus particles per milliliter of blood.^[60]

This response is accompanied by a marked drop in the numbers of circulating CD4⁺ T cells. This acute viremia is associated in virtually all patients with the activation of CD8⁺ T cells, which kill HIV-infected cells, and subsequently with antibody production, orseroconversion. The CD8⁺ T cell response is thought to be important in controlling virus levels, which peak and then decline, as the CD4⁺ T cell counts rebound. A good CD8⁺ T cell response has been linked to slower disease progression and a better prognosis, though it does not eliminate the virus.^[61]

The pathophysiology of AIDS is complex.^[62] Ultimately, HIV causes AIDS by depleting CD4⁺ T helper lymphocytes. This weakens the immune system and allows opportunistic infections. T lymphocytes are essential to the immune response and without them, the body cannot fight infections or kill cancerous cells. The mechanism of CD4⁺ T cell depletion differs in the acute and chronic phases.^[63]

During the acute phase, HIV-induced cell lysis and killing of infected cells by cytotoxic T cells accounts for CD4⁺ T cell depletion, although apoptosis may also be a factor. During the chronic phase, the consequences of generalized immune activation coupled with the gradual loss of the ability of the immune system to generate new T cells appear to account for the slow decline in CD4⁺ T cell numbers.

Although the symptoms of immune deficiency characteristic of AIDS do not appear for years after a person is infected, the bulk of CD4⁺ T cell loss occurs during the first weeks of infection, especially in the intestinal mucosa, which harbors the majority of the lymphocytes found in the body.^[64] The reason for the preferential loss of mucosal CD4⁺ T cells is that a majority of mucosal CD4⁺ T cells express the CCR5 coreceptor, whereas a small fraction of CD4⁺ T cells in the bloodstream do so.^[65]

HIV seeks out and destroys CCR5 expressing CD4⁺ cells during acute infection. A vigorous immune response eventually controls the infection and initiates the clinically latent phase. However, CD4⁺ T cells in mucosal tissues remain depleted throughout the infection, although enough remain to initially ward off life-threatening infections.

Continuous HIV replication results in a state of generalized immune activation persisting throughout the chronic phase.^[66] Immune activation, which is reflected by the increased activation state of immune cells and release of proinflammatory cytokines, results from the activity of several HIV gene products and the immune response to ongoing HIV replication. Another cause is the breakdown of the immune surveillance system of the mucosal barrier caused by the depletion of mucosal CD4⁺ T cells during the acute phase of disease.^[67]

This results in the systemic exposure of the immune system to microbial components of the gut’s normal flora, which in a healthy person is kept in check by the mucosal immune system. The activation and proliferation of T cells that results from immune activation provides fresh targets for HIV infection. However, direct killing by HIV alone cannot account for the observed depletion of CD4⁺ T cells since only 0.01–0.10% of CD4⁺ T cells in the blood are infected.

A major cause of CD4⁺ T cell loss appears to result from their heightened susceptibility to apoptosis when the immune system remains activated. Although new T cells are continuously produced by the thymus to replace the ones lost, the regenerative capacity of the thymus is slowly destroyed by direct infection of its thymocytes by HIV. Eventually, the minimal number of CD4⁺ T cells necessary to maintain a sufficient immune response is lost, leading to AIDS.

Diagnosis

A generalized graph of the relationship between HIV copies (viral load) and CD4 counts over the average course of untreated HIV infection; any particular individual's disease course may vary considerably.                     CD4⁺ T Lymphocyte count (cells/mm³)                     HIV RNA copies per mL of plasma

HIV testing is recommended is all those at high risk which includes anyone diagnosed with a sexually transmitted illness.^[12] The diagnosis of AIDS in a person infected with HIV is based on the presence of certain signs or symptoms. In many areas of the world a third of people only discover they have HIV when the disease is already advanced.^[12] In developing countries, the World Health Organization's staging system for HIV infection and disease is used (using clinical and laboratory data), and in developed countries theCDC's classification system is used. The stage of infection is typically determined by measuring the persons's CD4⁺ T cell count and viral load.

HIV test

Main article: HIV test

Most people infected with HIV develop antibodies (seroconvert) within three to twelve weeks of the initial infection.^[15] Diagnosis of primary HIV before serocoversion is done by measuring HIV-RNA or p24 antigen.^[15]

In 2001 many people were unaware that they are infected with HIV.^[68] Less than 1% of the sexually active urban population in Africa has been tested, and this proportion is even lower in rural populations. Furthermore, only 0.5% of pregnant women attending urban health facilities are counseled, tested or receive their test results. Again, this proportion is even lower in rural health facilities.^[68]

HIV tests are usually performed on venous blood. Many laboratories use fourth generation screening tests which detect anti-HIV antibody (IgG and IgM) and the HIV p24 antigen. The detection of HIV antibody or antigen in a patient previously known to be negative is evidence of HIV infection. Individuals whose first specimen indicates evidence of HIV infection will have a repeat test on a second blood sample to confirm the results.

Positive results obtained by PCR are confirmed by antibody tests.^[69] Routinely used HIV tests for infection in neonates and infants (i. e., people younger than 2 years),^[70] born to HIV-positive mothers, have no value because of the presence of maternal antibody to HIV in the child's blood. HIV infection can only be diagnosed by PCR, testing for HIV pro-viral DNA in the children's lymphocytes.^[71]

World Health Organization

Main article: WHO disease staging system for HIV infection and disease

The World Health Organization first proposed a definition for AIDS in 1986.^[13] A number of updates and expansions have take place between than and the most version in 2007.^[13] HIV is diagnosed via laboratory testing and than staged based on the presence of symptoms.^[13]

§  Primary HIV infection: May be either asymptomatic or associated with acute retroviral syndrome.^[13]

§  Stage I: HIV infection is asymptomatic

§  Stage II: includes minor mucocutaneous manifestations and recurrent upper respiratory tract infections

§  Stage III: includes unexplained chronic diarrhea for longer than a month, severe bacterial infections and tuberculosis of the lung as well as a CD4 count of less than 350/uL.^[13]

§  Stage IV or AIDS: includes toxoplasmosis of the brain, candidiasis of the esophagus, trachea, bronchi or lungs and Kaposi's sarcoma; these diseases are indicators of AIDS.

Center for Disease Control

Main article: CDC classification system for HIV infection

There are two main definitions for AIDS. The older definition using the diseases that were associated with it, for example,lymphadenopathy, the disease after which the discoverers of HIV originally named the virus.^[72][73] In 1993, the CDC expanded their definition of AIDS to include all HIV positive people with a CD4⁺ T cell count below 200 per µL of blood or 14% of all lymphocytes.^[74]The majority of new AIDS cases in developed countries use either this definition or the pre-1993 CDC definition. The AIDS diagnosis still stands even if, after treatment, the CD4⁺ T cell count rises to above 200 per µL of blood or other AIDS-defining illnesses are cured.

Screening

The South African government announced a plan to start screening for HIV in secondary schools by March 2011.^[75] This plan was cancelled due to concerns it would invade pupil's privacy, schools typically don't have the facilities to securely store such information, and schools generally do not have the capacity to provide counseling for HIV positive pupils. In South Africa, anyone over the age of 12 may request an HIV test without parental knowledge or consent. Some 80,000 pupils in three provinces were tested under this programme before it ended.^[76]

Prevention

Main article: Prevention of HIV/AIDS

AIDS Clinic, McLeod Ganj, Himachel Pradesh, India, 2010

Sexual contact

Consistent condom use reduces the risk of HIV transmission by approximately 80% over the long-term.^[77] Where one partner of a couple is infected, consistent condom use results in rates of HIV infection for the uninfected person of below 1% per year.^[78] Some data supports the equivalence of female condoms to latex condoms however the evidence is not definitive.^[79] The use of the spermicide nonoxynol-9may increase the risk of transmission due to the fact that it causes vaginal and rectal irritation.^[80] A vaginal gel containingtenofovir, a reverse transcriptase inhibitor, when used immediately before sex, reduce infection rates by approximately 40% among Africa women.^[81]

Circumcision in sub-Saharan Africa reduces the risk of HIV infection in heterosexual men by between 38 percent and 66 percent over two years.^[82] Based on these studies, the World Health Organization and UNAIDS both recommended male circumcision as a method of preventing female-to-male HIV transmission in 2007.^[83] Whether it protects against male-to-female transmission is disputed^[84][85] and whether it is of benefit indeveloped countries and among men who have sex with men is undetermined.^[86][87][88]Some experts fear that a lower perception of vulnerability among circumcised men may result in more sexual risk-taking behavior, thus negating its preventive effects.^[89] Women who have undergone female genital cutting have an increased risk of HIV.^[90]

Programs encouraging sexual abstinence do not appear to effect subsequent HIV risk.^[91] Evidence for a benefit from peer education is equally poor.^[92] Comprehensive sexual education provided at school may decrease high risk behavior.^[93] A substantial minority of young people continue to engage in high-risk practices despite HIV/AIDS knowledge, underestimating their own risk of becoming infected with HIV.^[94] It is not known if treating other sexually transmitted infections is effective in preventing HIV.^[36]

Pre exposure

Early treatment of HIV-infected people with antiretrovirals protected 96% of partners from infection.^[95][96] Pre-exposure prophylaxiswith a daily dose of the medications tenofovir with or without emtricitabine is effective in a number of groups including: men who have sex with men, couples where one is HIV positive, and young heterosexuals in Africa.^[81]

Universal precautions within the health care environment are believed to be effective in decreasing the risk of HIV.^[97] Intravenous drug use is an important risk factor and harm reduction strategies such as needle-exchange programmes and opioid substitution therapyappear effective in decreasing this risk.^[98]

Post exposure

A course of antiretrovirals administered within 48 to 72 hours after exposure to HIV positive blood or genital secretions is referred to aspost-exposure prophylaxis.^[81] The use of the single agent zidovudine reduces the risk of subsequent HIV infection fivefold following a needle stick injury.^[81] Treatment is recommended after sexual assault when the perpetrators is known to be HIV positive but is controversial when their HIV status is unknown.^[40] Current treatment regimes typical use lopinavir/ritonavir and lamivudine/zidovudineor emtricitabine/tenofovir and may decrease the risk further.^[81] The duration of treatment is usually four week^[99] and is associated with significant rates of adverse effects (for zidovudine ~70% including: nausea 24%, fatigue 22%, emotional distress 13%, headaches 9%).^[26]

Mother-to-child

Programs to prevent the transmission of HIV from mothers to children can reduce rates of transmission by 92-99%.^[48][98] This primarily involves the use of a combination of antivirals during pregnancy and after birth in the infant but also potentially include bottle feeding rather than breastfeeding.^[48][100] If replacement feeding is acceptable, feasible, affordable, sustainable and safe mothers should avoid breast-feeding their infants however exclusive breast-feeding is recommended during the first months of life if this is not the case.^[101] If exclusive breast feeding is carried out the provision of extended antiretroviral prophylaxis to the infant decreases the risk of transmission.^[102]

Vaccination

As of 2012 there is no effective vaccine for HIV or AIDS.^[103] A single trial of the vaccine RV 144 published in 2009 found a partial efficacy rate of ~30% and has stimulated optimism in the research community regarding developing a truly effective vaccine.^[104]Further trials of the vaccine are ongoing.^[105][106]

There is currently no cure or effective HIV vaccine. Treatment consists of high active antiretroviral therapy (HAART) which slows progression of the disease^[107] and as of 2010 more than 6.6 million people were taking them in low and middle income countries.^[6]Treatment also includes preventative and active treatment of opportunistic infections.

Antiviral therapy

Abacavir – a nucleoside analog reverse transcriptase inhibitor (NARTI or NRTI)

Current HAART options are combinations (or "cocktails") consisting of at least three medications belonging to at least two types, or "classes," of antiretroviral agents.^[108]Initially treatment is typically, a non-nucleoside reverse transcriptase inhibitor (NNRTI) plus two nucleoside analogue reverse transcriptase inhibitors (NRTIs).^[108] Typical NRTIs include: zidovudine (AZT) or tenofovir (TDF) and lamivudine (3TC) or emtricitabine (FTC).^[108]Combinations of agents which include a protease inhibitors (PI) are used if the above regime loses effectiveness.^[108]

When to start antiretroviral therapy is subject to debate.^[12][109] Both the World Health Organization, European guidelines and the United States recommends antiretrovirals in all adolescents, adults and pregnant women with a CD4 count less than 350/uL or those with symptoms regardless of CD4 count.^[12][108] This is supported by the fact that beginning treatment at this level reduces the risk of death.^[110] The United States in addition recommends them for all HIV infected people regardless of CD4 count or symptoms, however makes this recommendation with less confidence for those with higher counts.^[111]While the WHO also recommends treatment in those who are co-infected with tuberculosis and those with chronic active hepatitis B.^[108] Once treatment is begun it is recommended that it is continued without breaks or "holidays".^[12] Many people are diagnosed only after when treatment ideally should have begun.^[12]

The desired outcome of treatment is a long term plasma HIV-RNA count below 50 copies/mL.^[12] Levels to determine if treatment is effective are initially recommended after four weeks and once levels fall below 50 copies/mL checks every three to six months are typically adequate.^[12] Inadequate control is deemed to be greater than 400 copies/mL.^[12] Based on these criteria treatment is effective in more than 95% of people during the first year.^[12]

Benefits of treatment include a decreased risk of progression to AIDS and a decreased risk of death.^[112] In the developing world treatment also improves physical and mental health.^[113] With treatment there is a 70% reduced risk of aquiring tuberculosis.^[108]Addition benefits include a decreased risk of transmission of the disease to sexual partners and a decrease in mother to child transmission.^[108]

The effectiveness of treatment depends to a large part on compliance.^[12] Reasons for non-adherence include: poor access to medical care,^[114] inadequate social supports, mental illness and drug abuse.^[115] As well the complexity of treatment regimens (due to pill numbers and dosing frequency) and adverse effects may create intentional non-adherence.^[116] Adherence is however just as good in low income as high income countries.^[117]

Specific adverse events are related to the agent taken.^[118] Some relatively common adverse effects include: lipodystrophy syndrome,dyslipidemia, diabetes mellitus, diarrhea,^[118][119] and cardiovascular disease.^[120] Adverse effects are however less with some of the newer recommended treatments.^[12] Cost may be an issue with some medications being expensive^[121] however as of 2010, 47% of those who need them where taking them in low and middle income countries.^[6] Certain medications may be associated with birth defects and thus not suitable for women hoping to have children.^[12]

In children, treatment recommendations vary somewhat from adults. In the developing world, as of 2010, 23% of children who where in need of treatment had access.^[122] Both the World Health Organization and the United States recommends treatment in all children less than twelve months of age.^[123][124] The United States recommends in those between one year and five years of age treatment in those with HIV RNA counts of greater than 100,000 copies/mL, and in those more than five years treatments when CD4 counts are less than 500/ul.^[123]

Opportunistic infections

Measures to prevent opportunistic infections are effective in many people with HIV/AIDS. Treatment with antivirals often improves current, as well as decreases the risk of future, opportunistic infections.^[118] Vaccination against hepatitis A and B is advised for all people at risk of HIV before they become infected however may also be given after infection.^[125] Trimethoprim/sulfamethoxazoleprophylaxis between four to six weeks of age and finishing breastfeeding in infant born to HIV positive mothers is recommended in resource limited settings.^[122] It is also recommended to prevent PCP when peoples CD4 count is below 200 cells/uL and in those who have or have previously had PCP.^[126] People with substantial immunosuppression are also advised to receive prophylactic therapy fortoxoplasmosis and Cryptococcus meningitis.^[127] Appropriate preventive measures has reduced the rate of these infections by 50% between 1992 and 1997.^[128]

Alternative medicine

In the US, approximately 60% of people with HIV use various forms of complementary or alternative medicine.^[129] The effectiveness of most of these therapies however has not been established.^[130] With respect to dietary advice and AIDS some evidence has shown a benefit from micronutrient supplements.^[131] Evidence for supplementation with selenium is mixed with some tentative evidence of benefit.^[132] There is some evidence that vitamin A supplementation in children reduces mortality and improves growth.^[131] In Africa in nutritionally compromised pregnant and lactating women a multivitamin supplementation improved outcomes for both mothers and children.^[131] Dietary intake of micronutrients at RDA levels by HIV-infected adults is recommended by the World Health Organization.^[133][134] The WHO further states that several studies indicate that supplementation of vitamin A, zinc, and iron can produce adverse effects in HIV positive adults.^[134] There is not enough evidence to support the use of herbal medicines.^[135]

Prognosis

Disability-adjusted life year for HIV and AIDS per 100,000 inhabitants as of 2004.

no data   ≤ 10   10–25   25–50   50–100   100–500   500–1000

1000–2500   2500–5000   5000–7500   7500-10000   10000-50000   ≥ 50000

HIV/AIDS has become a chronic rather than an acutely fatal disease in many areas of the world.^[136] Prognosis varies between people and both the CD4 count and viral load are useful for predicted outcomes.^[15] Without treatment, average survival time after infection with HIV is estimated to be 9 to 11 years, depending on the HIV subtype.^[137] After the diagnosis of AIDS, if treatment is not available, survival ranges between 6 and 19 months.^[52][138] HAART and appropriate prevention of opportunistic infections reduces the death rate by 80%, and raises the life expectancy for a newly diagnosed young adult to 20–50 years.^{[136][139][140]} This is between two thirds^[139] and nearly that of the general population.^[12][141] If treatment is started late in the infection prognosis is not as good,^[12]for example if treatment is begun following the diagnosis of AIDS life expectancy is ~10–40 years.^[12][136] Half of infants born with HIV die before two years of age without treatment.^[122]

The primarily causes of death from HIV/AIDS is opportunistic infections and cancer both of which are frequently the result of the progressive failure of the immune system.^[128][142]Risk of cancer appears to increase once the CD 4 count get below 500/uL.^[12] The rate of clinical disease progression varies widely between individuals and has been shown to be affected by a number of factors such as a persons susceptibility and immune function,^[56] access to health care and co-infections,^[52][143] as well as which particular strain of the virus is involved.^[58][144]

Tuberculosis co-infection is one of the leading causes of sickness and death in those with HIV/AIDS being present in a third of all HIV infected people and resulting in 25% of HIV related deaths.^[145] HIV is also the most important risk factors for tuberculosis.^[146]Hepatitis C is another very common co-infection where each disease increases the progression of the other.^[147] The two most common cancers associated with HIV/AIDS are Kaposi's sarcoma and AIDS-related non-Hodgkin's lymphoma.^[142] Life expectancyhas fallen in the worst-affected countries due to HIV/AIDS; for example, in 2006 it was estimated that it had dropped from 65 to 35 years in Botswana.^[4]

Even with anti-retroviral treatment, over the long term HIV-infected people may experience neurocognitive disorders,^[148]osteoporosis,^[149] neuropathy,^[150] cancers,^[151][152] nephropathy,^[153] and cardiovascular disease.^[119] It is not clear whether these conditions result from the HIV infection itself or are adverse effects of treatment.

 

 

Epidemiology

Main article: Epidemiology of HIV/AIDS

Estimated prevalence of HIV among young adults (15–49) per country at the end of 2005.

HIV infections are considered pandemic by the World Health Organization (WHO).^[154] As of 2010 approximately 34 million people have HIV globally.^[6] Of these approximately 16.8 million are women and 3.4 million are less than 15 years old.^[6] It results in about 1.8 million death in 2010 down from 3.1 million in 2001.^[6]

Sub-Saharan Africa is the region most affected. In 2010, an estimated 68% (22.9 million) of all HIV cases and 66% of all deaths (1.2 million) occurred in this region.^[155] This means that about 5% of the adult population is infected^[156] and it is believed to be the cause of 10% of all deaths in children.^[157] Here in contrast to other regions women compose nearly 60% of cases.^[155] South Africa has the largest population of people with HIV of any country in the world at 5.9 million.^[155]

South & South East Asia is the second most affected; in 2010 this region contained an estimated 4 million cases or 12% of all people living with HIV resulting in approximately 250,000 deaths.^[156] Approximately 2.4 million of these cases are in India.^[155] Prevalence is lowest in Western and Central Europe at 0.2% and East Asia at 0.1%.^[156]

In 2008 in the United States approximately 1.2 million people were living with HIV, resulting in about 17,500 deaths. The Centre for Disease Control and Prevention estimated that in 2008 20% of infected Americans were unaware of their infection.^[158] In the United Kingdom as of 2009 there where approximately 86,500 cases which resulted in 516 deaths.^[159] In Canada as of 2008 there where about 65,000 cases which results in 53 deaths.^[160] Between the first recognition of AIDS in 1981 and 2009 it has led to nearly 30 million deaths.^[7]

Discovery

AIDS was first clinically observed in 1981 in the United States.^[161] The initial cases were a cluster of injection drug users and gay men with no known cause of impaired immunity showed symptoms of Pneumocystis carinii pneumonia (PCP), a rare opportunistic infection that was known to present itself in people with very compromised immune systems.^[162] Soon thereafter, additional gay men developed a previously rare skin cancer called Kaposi's sarcoma (KS).^[163][164] Many more cases of PCP and KS emerged, alerting U.S. Centers for Disease Control and Prevention (CDC) and a CDC task force was formed to monitor the outbreak.^[165]

In the beginning, the CDC did not have an official name for the disease, often referring to it by way of the diseases that were associated with it, for example, lymphadenopathy, the disease after which the discoverers of HIV originally named the virus.^[72][73]They also used Kaposi's Sarcoma and Opportunistic Infections, the name by which a task force had been set up in 1981.^[166] In the general press, the term GRID, which stood for gay-related immune deficiency, had been coined.^[167] The CDC, in search of a name, and looking at the infected communities coined “the 4H disease, ” as it seemed to single out Haitians, homosexuals, hemophiliacs, and heroin users.^[168] However, after determining that AIDS was not isolated to the gay community,^[166] the term GRID became misleading and AIDS was introduced at a meeting in July 1982.^[169] By September 1982 the CDC started using the name AIDS, and properly defined the illness.^[170]

Robert Gallo, co-discoverer of HIV

In 1983, two separate research groups led by Robert Gallo and Luc Montagnier independently declared that a novel retrovirus may have been infecting AIDS patients, and published their findings in the same issue of the journal Science.^[171][172] Gallo claimed that a virus his group had isolated from an AIDS patient was strikingly similar in shape to other human T-lymphotropic viruses(HTLVs) his group had been the first to isolate. Gallo's group called their newly isolated virus HTLV-III. At the same time, Montagnier's group isolated a virus from a patient presenting with swelling of the lymph nodes of the neck and physical weakness, two classic symptoms of AIDS. Contradicting the report from Gallo's group, Montagnier and his colleagues showed that core proteins of this virus were immunologically different from those of HTLV-I. Montagnier's group named their isolated virus lymphadenopathy-associated virus (LAV).^[165] HIV was chosen as a compromise between the two claims (LAV and HTLV-III).

Origins

HIV is thought to have originated in non-human primates in sub-Saharan Africa and was transferred to humans late in the 19th or early in the 20th century.^{[173][174][175]} The first paper recognizing a pattern of opportunistic infections characteristic of AIDS was published in 1981.^[162]

Both HIV-1 and HIV-2 are believed to have originated in West-Central Africa and to have jumped species (a process known aszoonosis) from non-human primates to humans. HIV-1 appears to have originated in southern Cameroon through the evolution of SIV(cpz), a simian immunodeficiency virus (SIV) that infects wild chimpanzees (HIV-1 descends from the SIVcpz endemic in the chimpanzee subspecies Pan troglodytes troglodytes).^[176][177] The closest relative of HIV-2 is SIV(smm), a virus of the sooty mangabey (Cercocebus atys atys), an Old World monkey living in litoral West Africa (from southern Senegal to western Ivory Coast).^[178] New World monkeys such as the owl monkey are resistant to HIV-1 infection, possibly because of a genomic fusion of two viral resistance genes.^[179] HIV-1 is thought to have jumped the species barrier on at least three separate occasions, giving rise to the three groups of the virus, M, N, and O.^[180]

There is evidence that humans who participate in bushmeat activities, either as hunters or as bushmeat vendors, commonly acquire SIV.^[181] However, SIV is a weak virus, it is typically suppressed by the human immune system within weeks of infection. It is thought that several transmissions of the virus from individual to individual in quick succession are necessary to allow it enough time to mutate into HIV.^[182] Furthermore, due to its relatively low person-to-person transmission rate, it can only spread throughout the population in the presence of one or more of high-risk transmission channels, which are thought to have been absent in Africa prior to the 20th century.

Specific proposed high-risk transmission channels, allowing the virus to adapt to humans and spread throughout the society, depend on the proposed timing of the animal-to-human crossing. Genetic studies of the virus suggest that the most recent common ancestor of the HIV-1 M group dates back to circa 1910.^[183] Proponents of this dating link the HIV epidemic with the emergence of colonialismand growth of large colonial African cities, leading to social changes, including a higher degree of sexual promiscuity, the spread ofprostitution, and the concomitant high frequency of genital ulcer diseases (such as syphilis) in nascent colonial cities.^[184] While transmission rates of HIV during vaginal intercourse, are low under regular circumstances, they are increased many fold if one of the partners suffers from an sexually transmitted infection resulting in genital ulcers. Early 1900s colonial cities were notable due to their high prevalence of prostitution and genital ulcers, to the degree that, as of 1928, as many as 45% of female residents of easternKinshasa were thought to have been prostitutes, and, as of 1933, around 15% of all residents of the same city were infected by one of the forms of syphilis.^[184]

An alternative view holds that unsafe medical practices in Africa during years following World War II, such as unsterile reuse of single use syringes during mass vaccination, antibiotic and anti-malaria treatment campaigns, were the initial vector that allowed the virus to adapt to humans and spread.^{[182][185][186]}

The earliest well documented case of HIV in a human dates back to 1959 in the Congo.^[187] The virus may have been present in the United States as early as 1966,^[188] but the vast majority of infections occurring outside sub-Saharan Africa (including the U.S.) can be traced back to a single unknown individual who got infected with HIV in Haiti and then brought the infection to the United States some time around 1969.^[189] The epidemic then rapidly spread among high-risk groups (initially, sexually promiscuous gay men). By 1978, the prevalence of HIV-1 among gay male residents of New York and San Francisco was estimated at 5%, suggesting that several thousand individuals in the country had been infected by then.^[189]

Society and culture

Stigma

Ryan White became a poster child for HIV after being expelled from school because of his infection.

Main article: Discrimination against people with HIV/AIDS

AIDS stigma exists around the world in a variety of ways, including ostracism, rejection, discrimination and avoidance of HIV infected people; compulsory HIV testing without prior consent or protection of confidentiality; violence against HIV infected individuals or people who are perceived to be infected with HIV; and the quarantine of HIV infected individuals.^[190] Stigma-related violence or the fear of violence prevents many people from seeking HIV testing, returning for their results, or securing treatment, possibly turning what could be a manageable chronic illness into a death sentence and perpetuating the spread of HIV.^[191]

AIDS stigma has been further divided into the following three categories:

§  Instrumental AIDS stigma—a reflection of the fear and apprehension that are likely to be associated with any deadly and transmissible illness.^[192]

§  Symbolic AIDS stigma—the use of HIV/AIDS to express attitudes toward the social groups or lifestyles perceived to be associated with the disease.^[192]

§  Courtesy AIDS stigma—stigmatization of people connected to the issue of HIV/AIDS or HIV- positive people.^[193]

Often, AIDS stigma is expressed in conjunction with one or more other stigmas, particularly those associated with homosexuality, bisexuality, promiscuity, prostitution, and intravenous drug use.

In many developed countries, there is an association between AIDS and homosexuality or bisexuality, and this association is correlated with higher levels of sexual prejudice such as anti-homosexual/bisexual attitudes.^[194] There is also a perceived association between AIDS and all male-male sexual behavior, including sex between uninfected men.^[192]

Economic impact

Main article: Economic impact of HIV/AIDS

Changes in life expectancy in some hard-hit African countries.                     Botswana                     Zimbabwe                     Kenya                     South Africa                     Uganda

HIV/AIDS affects the economics of both individuals and countries.^[157] The gross domestic product of the most effected countries have decreased due to the lack of human capital.^[195][157] Without proper nutrition, health care and medicine, large numbers of people die from AIDS-related complications. They will not only be unable to work, but will also require significant medical care. It is estimated that as of 2007 there where 12 million AIDS orphans.^[157] Many are cared for by elderly grandparents.^[196]

By affecting mainly young adults, AIDS reduces the taxable population, in turn reducing the resources available for public expenditures such as education and health services not related to AIDS resulting in increasing pressure for the state's finances and slower growth of the economy. This results in a slower growth of the tax base, an effect that is reinforced if there are growing expenditures on treating the sick, training (to replace sick workers), sick pay and caring for AIDS orphans. This is especially true if the sharp increase in adult mortality shifts the responsibility and blame from the family to the government in caring for these orphans.^[196]

On the level of the household, AIDS results in both loss of income and increased spending on healthcare. This leaves less income to spend education. A study in Côte d'Ivoire showed that households with an HIV/AIDS patient spent twice as much on medical expenses as other households.^[197]

Religion and AIDS

Main article: Religion and HIV/AIDS

The topic of religion and AIDS has become highly controversial in the past twenty years, primarily because many prominent religious leaders have publicly declared their opposition to the use of condoms.^[198][199] However, there is a growing openness to faith-based methods due to the failure rates associated with condoms.^[199] The religious approach to prevent the spread of AIDS according to a report by American health expert Matthew Hanley titled The Catholic Church and the Global Aids Crisis argues that cultural changes are needed including a re-emphasis on fidelity within marriage and sexual abstinence outside of it.^[199]

In addition to prevention, some religious groups have interrupted the treatment of AIDS. According to the African Health Policy Network, some churches in London claim that prayer will cure AIDS and the Hackney-based Centre for the Study of Sexual Health and HIV reports that several people have stopped taking their medication, sometimes on the direct advice of their pastor, leading to a number of deaths.^[200] The Synagogue Church Of All Nations advertise an "anointing water" to promote God's healing, although the group deny advising people to stop taking medication,^[200] and US patent application 2001051133 similarly suggests that intravenous pure distilled water will eradicate HIV through the mercy of God.^[201]

Notable cases

One of the first high profile cases of AIDS was the American Rock Hudson, a gay actor who had been married and divorced earlier in life, who died on 2 October 1985 having announced that he was suffering from the virus on 25 July that year. It had been diagnosed during 1984.^[202] A notable British casualty of AIDS that year was Nicholas Eden, a gay Member of Parliament and son of the late prime minister Anthony Eden.^[203][204] The virus claimed perhaps its most famous victim yet on November 24, 1991, when British rock star Freddie Mercury, lead singer of the band Queen, died from an AIDS related illness having only announced that he was suffering from the illness the previous day.^[205] However he had been diagnosed as HIV positive during 1987.^[206] One of the first high profile heterosexual victims of the virus was Arthur Ashe, the American tennis player. He was diagnosed as HIV positive on 31 August 1988, having contracted the virus from blood transfusions during heart surgery earlier in the 1980s. Further tests within 24 hours of the initial diagnosis revealed that Ashe had AIDS, but he did not tell the public about his diagnosis until April 1992.^[207] He died, aged 49, as a result on 6 February 1993.^[208]

Denial, conspiracies and misconceptions

Main articles: AIDS denialism and Misconceptions about HIV/AIDS

A small group of individuals continue to dispute the connection between HIV and AIDS,^[209] the existence of HIV itself, or the validity of HIV testing and treatment methods.^[210][211] These claims, known as AIDS denialism, have been examined and rejected by the scientific community.^[212] However, they have had a significant political impact, particularly in South Africa, where the government's official embrace of AIDS denialism was responsible for its ineffective response to that country's AIDS epidemic, and has been blamed for hundreds of thousands of avoidable deaths and HIV infections.^{[213][214][215]}

Operation INFEKTION was a worldwide Soviet active measures operation to spread information that the United States had created HIV/AIDS. Surveys show that a significant number of people believed – and continue to believe – in such claims.^[216]

There are many misconceptions about HIV and AIDS. Three of the most common are that AIDS can spread through casual contact, that sexual intercourse with a virgin will cure AIDS, and that HIV can infect only homosexual men and drug users. Other misconceptions are that any act of anal intercourse between two uninfected gay men can lead to HIV infection, and that open discussion of homosexuality and HIV in schools will lead to increased rates of homosexuality and AIDS.^[217][218]

Research

"AIDS research" redirects here. For the journal formerly known as AIDS Research, see AIDS Research and Human Retroviruses.

Research to improve current treatments includes decreasing side effects of current drugs, further simplifying drug regimens to improve adherence, and determining the best sequence of regimens to manage drug resistance. However, only a vaccine is thought to be able to halt the pandemic. This is because a vaccine would cost less, thus being affordable for developing countries, and would not require daily treatment.^[219] However, after over 20 years of research, HIV-1 remains a difficult target for a vaccine.^[219][220]

Stem cell transplantation

In 2007, Timothy Ray Brown,^[221] a 40-year-old HIV-positive man, was given a stem cell transplant as part of his treatment for acute myeloid leukemia (AML).^[222] A second transplant was made a year later after a relapse. The donor was chosen not only for genetic compatibility but also for being homozygous for a CCR5-Δ32 mutation that confers resistance to HIV infection.^[223][224] After 20 months without antiretroviral drug treatment, it was reported that HIV levels in Brown's blood, bone marrow, and bowel were below the limit of detection.^[224] The virus remained undetectable over three years after the first transplant.^[222] Although the researchers and some commentators have characterized this result as a cure, others suggest that the virus may remain hidden in tissues^[225] such as the brain (a viral reservoir).^[226] Stem cell treatment remains investigational because of its anecdotal nature, the disease and mortality risk associated with stem cell transplants, and the difficulty of finding suitable donors.^[225][227]

Immunomodulatory agents

Complementing efforts to control viral replication, immunotherapies that may assist in the recovery of the immune system have been explored in past and ongoing trials, including IL-2and IL-7.^[228]

The failure of vaccine candidates to protect against HIV infection and progression to AIDS has led to a renewed focus on the biological mechanisms responsible for HIV latency. A limited period of therapy combining anti-retrovirals with drugs targeting the latent reservoir may one day allow for total eradication of HIV infection.^[229] Researchers have discovered an abzyme that can destroy the proteingp120 CD4 binding site. This protein is common to all HIV variants as it is the attachment point for B lymphocytes and subsequent compromising of the immune system.^[230]