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HIV/AIDS

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AIDS (Acquired immunodeficiency syndrome or Acquired immune deficiency syndrome) is an infection with a retrovirus called HIV or Human immunodeficiency virus. In a process still imperfectly understood, HIV infects the CD4 cells (also called T4 or T-helper cells) of the immune system. This loss of cellular immunity results in one or more AIDS defining clinical condition.

AIDS is incurable. AIDS typically develops within ten years following HIV infection. Without antiretroviral treatment, for an AIDS defining clinical condition death usually occurs soon after diagnosis.

AIDS was first identified in the United States in 1981, from the initial case reports of opportunistic illnesses caused by a then unknown agent in a few large cities. [1] Further research has indicated it originally appeared in Africa during the 1930s, when chimpanzee hunters were infected with simian immunodeficiency virus (SIV). In 2004, about 60 percent of people with AIDS live in Africa, mostly heterosexual women and men. In the United States and Europe, AIDS remains confined to the original risk groups of men who have sex with men, and intravenous drug users.

In December 2004, UNAIDS and the World Health Organization estimated that between 39 and 44 million people around the world were infected with HIV and between 2.8 and 3.5 million people with AIDS died during 2004. [2]

In the United States, 711,344 AIDS cases were reported from 1981 through to June 30, 1999. [3]

File:Red ribbon.jpg
The Red Ribbon symbol is used internationally to represent the fight against AIDS.

Symptoms

HIV is transmitted by bodily fluids, such as blood, semen, breast milk, and vaginal secretions. It causes disease by infecting CD4+ T cells, a type of leukocyte (white blood cell) that normally coordinates the immune response to infection and cancer. When a person's CD4+ T cell count decreases sufficiently he or she is prone to a range of diseases that a healthy person's body is normally able to fight. These diseases include cancers and opportunistic infections, which are usually the cause of death in persons with AIDS. HIV may also infect brain cells, causing some neurological disorders.

Diagnostic criteria

A person is diagnosed with AIDS when his or her immune system is seriously compromised and manifestations of HIV infection are severe. The U.S. Centers for Disease Control and Prevention CDC currently defines AIDS in an adult or adolescent age 13 years or older as the presence of one of 26 conditions indicative of the immune system suppression associated with HIV infection, such as pneumonia caused by Pneumocystis carinii PCP, a condition extraordinarily rare in people without HIV infection [4]. Most other AIDS-defining conditions are also opportunistic infections; which rarely cause harm in healthy individuals. A diagnosis of AIDS also is given to HIV-infected individuals when their CD4+ T-cell count falls below 200 cells/cubic millimeter (mm3) of blood. Healthy adults usually have CD4+ T-cell counts of 600-1,500/mm3 of blood. In HIV-infected children younger than 13 years, the CDC definition of AIDS is similar to that in adolescents and adults, except for the addition of certain infections commonly seen in pediatric patients with HIV. [5].

In the 1980s and 1990s, for the purposes of epidemiological reporting, many developing countries used a purely symptomatic definition of AIDS known as the Bangui definition. This definition was a practical tool even for countries unable to afford antibody testing, but according to the WHO [6] this test has the disadvantage that HIV-negative tuberculosis patients may be classed as having AIDS due to the similarity in symptoms. However, by 1997, most developing nations also required a positive HIV antibody test for diagnosis[7]. If antibody testing is available, the WHO currently recommends a revised definition requiring a positive HIV antibody test and the presence of one of a slightly wider range of diseases [8].

Origins of HIV

HIV is closely related to the simian immunodeficiency viruses (SIV). The SIV are lentiviruses, like HIV, and are endemic to many African monkeys and apes, in which they are largely asymptomatic. Most scientists believe that one or more SIV were transferred from animals to humans at some time during the early 20th century. Research conducted in 1999 at the University of Alabama found that HIV-1 was very similar to the chimpanzee SIV (SIVcpz). The exact animal source, time, and location of the transfer (or indeed, how many transfers there were) is not currently known and is the subject of research and controversy. It may be possible that both humans and chimpanzees were infected from a third source.

File:HIV Viron.png
Diagram of the HIV virus.

The natural transfer hypothesis proposes that SIV was transferred to humans due to the natural interaction between human and primate populations. The hunting of monkeys for bushmeat, the so-called "cut hunter" theory, is one possible route, particularly as the bushmeat trade is known to result in around eight new zoonotic transmissions annually. Another is the consumption of raw animal flesh, supposing oral transmission.

Studies suggest that the virus spread initially in West Africa, but it is possible that there were several separate initial sources, corresponding to the different strains of HIV (HIV-1 and HIV-2). The earliest human fluid sample known to contain HIV was taken in 1959 from a British sailor, who apparently contracted it in what is now the Democratic Republic of the Congo. Other early samples include one from an American male who died in 1969, and a Norwegian sailor in 1976. It is believed that the virus was spread via sexual activity, possibly including with prostitutes, in Africa's rapidly growing urban areas. As unwittingly infected people traveled the virus spread from one city to another, and air travelers carried the virus to other continents.

Some researchers have suggested that HIV may have been introduced by the United Nations oral polio vaccination program in Africa during the late 1950s. The OPV AIDS hypothesis argues that the use of monkey and chimpanzee organs to prepare vaccines, such as the polio vaccine, provides a possible mechanism for the introduction of SIV into humans, particularly considering that the vaccines were administered to a million people, many of them young infants with weak immune systems. This view is very much a minority one in the HIV research community.

Current medical understanding of AIDS

Currently the most common ways to contract HIV are via unprotected sexual activity and the sharing of needles by users of intravenous drugs. The virus is rarely transmitted from mother to child in the womb, but HIV can be transmitted during childbirth or through breastfeeding. Blood transfusions and the use of blood products to treat haemophilia have been major routes of infection in the past, leading to stricter screening procedures (but despite these new measures such cases are still reported occasionally).

Not every patient who is infected with HIV is considered to have AIDS. The criteria for a diagnosis of AIDS can vary from region to region, but a diagnosis typically requires either:

  • an absolute CD4 cell count below 200 per cubic millimetre, or
  • the presence of opportunistic infections, caused by agents usually unable to induce diseases in healthy people

A person who is infected with HIV is said to be HIV+ (HIV positive or seropositive) and is sometimes referred to as a PWH, or Person With HIV. An uninfected individual is said to be HIV- (HIV negative or seronegative). HIV+ individuals are frequently unaware of their HIV status. Persons with AIDS (PWAs) are also said to be HIV+, and PWHs and PWAs are sometimes collectively referred to as PWAs or PWH/As. In recent years the more optimistic term "People Living With AIDS" (PLWAs) has come to be preferred by AIDS activist groups and many people with AIDS themselves.

HIV daughter particles being shed from an infected T cell.

Primary infection with HIV is called seroconversion, and may be accompanied by what is called "seroconversion illness" (an earlier term was "AIDS prodrome"). Symptoms of seroconversion illness include mild flu-like symptoms such as fever, aching muscles and joints, sore throat, and swollen glands (lymph nodes), but may also include other symptoms such as rash. Not every person who seroconverts experiences seroconversion illness, and there are people who experience no symptoms at all at this stage.

Regardless of the presence or absence of initial symptoms, all newly infected individuals become asymptomatic (symptom-free). The newly infected patient is actually most infectious during the seroconversion illness as it is during this time that the HIV viral load in the blood plasma is highest. At this stage, the virus is still multiplying rapidly, unchecked, because the body has not yet started to produce antibodies to the virus in sufficient quantities to reach an equilibrium.

During the asymptomatic stage, billions of HIV particles are produced every day accompanied by a decline, at variable rates, in the number of CD4+ T cells. The virus is not only present in the blood, but also throughout the body, particularly in the lymph nodes, brain, and genital secretions. During this stage, the body's immune system is actively trying to fight off the HIV infection but, for the vast majority of infected people who are not receiving treatment, the immune response is insufficient as the virus directly attacks cells of the immune system and mutates rapidly.

The time from infection with HIV to a diagnosis of AIDS varies. Some patients develop symptoms within a few months of infection, while others are known to have remained completely asymptomatic for as long as 20 years. These people who remain asymptomatic are often called Long-term AIDS nonprogressors. Why these nonprogressors remain AIDS-free, and why different people advance at various rates, is currently unknown, and is the subject of ongoing study. The average time of progression from initial infection to AIDS is eight to ten years in the absence of treatment.

Treatments and vaccines

There is currently no cure or vaccine for HIV or AIDS. Newer treatments, however, have played a part in delaying the onset of AIDS, on reducing the symptoms, and extending patients' life spans. Over the past decade the success of these anti-retroviral treatments in prolonging, and improving, the quality of life for people with AIDS has improved dramatically.

Current optimal treatment options consist of combinations ("cocktails") of two or more types of anti-retroviral agents such as two nucleoside analogue reverse transcriptase inhibitors (NRTIs), and a protease inhibitor or a non nucleoside reverse transcriptase inhibitor (NNRTI). Patients on such treatments have been known to repeatedly test "undetectable" (that is, negative) for HIV, but discontinuing therapy has thus far caused all such patients' viral loads to promptly increase. There is also concern with such regimens that drug resistance will eventually develop. In recent years the term HAART (highly-active anti-retroviral therapy) has been commonly used to describe this form of treatment. The majority of the world's infected individuals, unfortunately, do not have access to medications and treatments for HIV and AIDS.

There is ongoing research into developing a vaccine for HIV and in developing new anti-retroviral drugs. Human trials are currently underway. Research to improve current treatments includes simplifying current drug regimens to improve adherence and in decreasing side effects.

VIRxSYS Corporation has developed an innovative HIV lentiviral vector, called VRX496, that can be used to combat the HIV virus. The method has entered Phase I clinical trials, and it is the first-ever use of a lentiviral vector in humans. If results are positive, the method might be proven an effective cure for the AIDS disease.

Ever since AIDS entered the public consciousness, various forms of alternative medicine have been used to treat its symptoms. In the first decade of the epidemic when no useful conventional treatment was available, a large number of PWAs experimented with alternative therapies of various kinds, including massage, herbal and flower remedies and acupuncture, to either combat the virus or to relieve related symptoms. None of these were shown to have any genuine or long-term effect on the virus in controlled trials, but they may have had other quality of life-enhancing effects on individual users. Interest in these therapies has declined over the past decade as conventional treatments have improved. They are still used by some people with AIDS who do not believe that HIV causes AIDS. Alternative therapies such as massage, acupuncture and herbal medicine are still used by many sufferers in conjunction with other treatments, mainly to treat symptoms such as pain and loss of appetite. People with AIDS, like people with other illnesses such as cancer, also sometimes use marijuana to treat pain, combat nausea and stimulate appetite.


Current status

AIDS is a global epidemic that exists on every continent except Antartica. UNAIDS estimates that in 2003, 40 million people were infected with AIDS, 3 million died due to AIDS (with a total of 19 million dead since 1980) and 5 million were newly infected with HIV [9]. The majority of AIDS cases occur in Sub-Saharan Africa, in which 8% of the adult population is infected. South & South East Asia are the second most affected areas, with 15% of global AIDS cases. Children accounted for 500,000 of the AIDS deaths. These numbers have led some experts to call AIDS the deadliest pandemic in human history since the Black Death that ravaged Europe and western Asia in the 14th century and the introduction of smallpox and other Eurasian diseases to the Americas in the 16th century.

In Western countries the infection rate of HIV has slowed somewhat, due to the widespread adoption of safe sex practices by most of the sexually active population (including gay men) and (to a lesser extent) the existence of needle exchanges and campaigns to educate intravenous drug users about the dangers of sharing needles. The spread of infection among heterosexuals in western countries has also been much slower than originally feared, possibly because HIV is less readily transmissible through vaginal sex without other concurrent sexually transmitted diseases than was initially believed.

In some populations, however, such as young urban gay men, infection rates began to show signs of rising again from the late 1990s. In Britain the number of people diagnosed with HIV increased 26% from 2000 to 2001. Similar trends have been seen in the United States and Australia, and are attributed to "AIDS fatigue" among younger gay men who have no memory of the worst phase of the epidemic in the 1980s as well as "condom fatigue" among those who have grown tired of and dissillusioned with the unrelenting safer sex message. This trend is of major concern to public health workers. AIDS continues to be a problem with illegal sex workers and injection drug users. On the other hand, the death rate from AIDS in all Western countries has fallen sharply, as new AIDS therapies have proven to be an effective (if expensive) means of suppressing HIV.

In developing countries, in particular Sub-Saharan Africa, however, poor economic conditions (leading to the use of dirty needles in healthcare clinics) and lack of sex education means continued high infection rates (see AIDS in Africa). In some countries in Africa 25% or more of the working adult population is HIV-positive; in Botswana alone the figure is 35.8% (1999 estimate — source World Press Review). The situation in South Africa, where President Thabo Mbeki shares the views of the AIDS denialists, is also deteriorating rapidly, with 4.7 million infections in 2002. Also suffering heavily are Nigeria and Ethiopia, which had 3.7 million and 2.4 million people infected respectively in 2003. On the other hand Uganda, Zambia, and Senegal have initiated prevention programs to reduce their HIV infection rates, with varying degrees of success.

Latin America and the Caribbean had just over 2.2 million infected persons in 2003, with modes of transmission and infection rates varying widely. The infection rates are highest in Central America and the Caribbean, where heterosexual transmission is fairly common. In Mexico, Brazil, Colombia, and Argentina, drug injection and homosexual activity are the main modes of transmission, but there is concern that heterosexual activity may soon become a primary method of spreading the virus. Brazil recently began a comprehensive AIDS prevention and treatment program to keep the AIDS virus in check, including the production of generic versions of anti-retroviral drugs.

AIDS infection rates are also rising steadily in Asia, with over 7.5 million infections by 2003. In July 2003, the estimated number of HIV+ individuals in India was about 4.6 million, roughly 0.9% of the working adult population. In China, the number was estimated at 1 million to 1.5 million, with some estimates going much higher. Both countries have growing epidemics spread by large numbers of urban sex workers (a technical term for prostitute) and intravenous drug use. China also suffers from an epidemic in some of its rural areas, where large numbers of farmers, especially in Henan province, participated in sloppy procedures for blood transfusions; estimates of those infected are in the tens of thousands. AIDS seems to be under control in Thailand and Cambodia, but new infections occur in those nations at a steady rate.

There is also growing concern about a rapidly growing epidemic in Eastern Europe and Central Asia, where an estimated 1.7 million people were infected by January 2004. The rate of HIV infections rose rapidly from the mid-1990s, due to social and economic collapse, increased levels of intravenous drug use and increased numbers of prostitutes. By 2004 the number of reported cases in Russia was over 257,000, according to the World Health Organization, up from 15,000 in 1995 and 190,000 in 2002; some estimates claim the real number is up to five times higher, over 1 million. There are predictions that the infection rate in Russia will continue to rise quickly, since education there about AIDS is almost non-existent. Ukraine and Estonia also had growing numbers of infected people, with estimates of 500,000 and 3,700 respectively in 2004.

Prevention

Despite widely publicised fears about the possible "casual transmission" of HIV and AIDS, the risk of infection is virtually eliminated by following simple precautions, such as abstaining from sexual activity outside a definitely monogamous relation with a seronegative partner, and avoiding blood transfusions with unsafe blood.

The only proven cause of transmission is the exchange of bodily fluids, in particular blood and genital secretions. HIV cannot be transmitted by breathing, via casual contact such as touching, holding or shaking hands, hugging and kissing, by mutual masturbation, or by sharing cooking and eating utensils, dishes, cups and glasses. It is possible that HIV could be transmitted through open-mouthed kissing if both partners had bleeding oral sores, but no such case has been documented and the possibility of transmission in this way is considered very unlikely as saliva contains much lower concentrations of HIV than, for example, semen.

Stop AIDS Project marchers at San Francisco Pride 2004.

HIV is not a hardy organism; the virus dies within about twenty minutes once it is outside a human body. Thus, for example blood or semen stains quickly become non-infectious and are no cause for concern.

HIV transmission via sexual activity has been recorded from male to male, male to female, female to female and female to male. "Health experts around the world urge people to use condoms to protect themselves from HIV and a host of sexually transmitted infections." [10]. Although condoms are not 100% effective against pregnancy or disease transmission, it has been repeatedly shown that HIV cannot pass through latex condoms. All major brand condoms are electrically tested during production to ensure they have no microscopic holes. However packaged condoms do not last indefinitely, old condoms have a higher risk of tearing, thus they should not be used after the date given on the package.

Anal sex, because of the delicacy of the tissues in the anus and the ease with which they can tear, is considered the highest-risk sexual activity, but condoms are recommended for vaginal sex as well. Condoms should be used only once, and then thrown away and a new condom used each time. Because of the risk of tearing (both of the condom and of skin and mucous membranes), the use of water-based lubricants is recommended. Oil-based sexual lubricants should not be used with condoms as they can cause tears in the condom material by weakening the latex.

In terms of HIV transmission, oral sex is considered a lower risk than vaginal or anal sex. The relative lack of definitive research on the subject, coupled with conflicting public information and cultural influences have caused many to believe, incorrectly, that oral sex is safe. Although the actual risk factor of oral HIV transmission is unknown, there are documented cases of HIV transmission through both insertive and receptive (male) oral sex. One study concluded that 7.8% of recently infected men in San Francisco were probably infected through oral sex. However, a study of Spanish men who knowingly engaged in oral sex with HIV+ partners identified no cases of oral transmission. Part of the reason for such apparently conflicting evidence is that identifying oral transmission cases is problematic. Most HIV+ persons engaged in other types of sexual activity prior to infection, thus making it difficult or impossible to isolate oral transmission. Factors such as mouth sores, etc., are also difficult to decouple from transmission between "healthy" persons. It is usually recommended not to take semen or preseminal fluid into the mouth. The use of condoms for oral sex (or dental dams for cunnilingus) further reduces the potential risk.

HIV is known to be transmitted via the sharing of needles by users of intravenous drugs, and this is one of the most common methods of transmission. All AIDS-prevention organisations advise drug-users not to share needles and to use a new or properly sterilized needle for each injection. Information on cleaning needles using bleach is available from health care and addiction professionals and from needle exchanges. In the United States and other western countries, clean needles are available free in some cities, at needle exchanges or safe injection sites.

Medical workers who follow universal precautions or body substance isolation such as wearing latex gloves when giving injections or handling bodily wastes or fluids, and washing the hands frequently, can prevent the spread of HIV from patients to workers, and from patient to patient. The risk of being infected with HIV from a single prick with a needle that has been used on an HIV infected person is thought to be less than 1 in 200. Post-exposure prophylaxis with anti-HIV drugs can further reduce that small risk.

Several studies have shown that circumcised men may be slightly less likely to contract HIV. Alternatively, there are studies which show nations with high circumcision rates have more AIDS overall than those with low rates. One theory is that cells in the foreskin, which are removed during circumcision, act as so-called "HIV receptors". The difference at present appears to be very slight, and could be a result of cultural and hygiene differences rather than circumcision. It is unlikely that these findings will lead to an increase in circumcisions carried out on newborns, which are currently performed on most infant boys in the United States. Being circumcised should not be taken as having immunity to HIV.

There is now some evidence that treatment of already-infected people with antiretroviral drugs may reduce the transmission of HIV infection to their sexual partners, independently of other safer-sex precautions [11]. This may imply that aggressively treating existing HIV cases, in addition to protecting the uninfected population through education and safer-sex programs, may be more effective at preventing the spread of HIV that either of these alone.

References

External links

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