MYTH: HIV antibody testing is unreliable.

FACT: Diagnosis of infection using antibody testing is one of the best-established concepts in medicine. HIV antibody tests exceed the performance of most other infectious disease tests in both sensitivity (the ability of the screening test to give a positive finding when the person tested truly has the disease ) and specificity (the ability of the test to give a negative finding when the subjects tested are free of the disease under study). Current HIV antibody tests have sensitivity and specificity in excess of 98% and are therefore extremely reliable (WHO, 1998; Sloand et al. JAMA 1991;266:2861).

Progress in testing methodology has also enabled detection of viral genetic material, antigens and the virus itself in body fluids and cells. While not widely used for routine testing due to high cost and requirements in laboratory equipment, these direct testing techniques have confirmed the validity of the antibody tests.

MYTH: There is no AIDS in Africa . AIDS is nothing more than a new name for old diseases.

FACT: The diseases that have come to be associated with AIDS in Africa – such as wasting syndrome, diarrheal diseases and TB – have long been severe burdens there. However, high rates of mortality from these diseases, formerly confined to the elderly and malnourished, are now common among HIV-infected young and middle-aged people, including well-educated members of the middle class (UNAIDS, 2000).

For example, in a study in Cote d'Ivoire , HIV-seropositive individuals with pulmonary tuberculosis (TB) were 17 times more likely to die within six months than HIV-seronegative individuals with pulmonary TB (Ackah et al. Lancet 1995; 345:607). In Malawi , mortality over three years among children who had received recommended childhood immunizations and who survived the first year of life was 9.5 times higher among HIV-seropositive children than among HIV-seronegative children. The leading causes of death were wasting and respiratory conditions (Taha et al. Pediatr Infect Dis J 1999;18:689). Elsewhere in Africa , findings are similar.

MYTH: HIV cannot be the cause of AIDS because researchers are unable to explain precisely how HIV destroys the immune system.

FACT: A great deal is known about the pathogenesis of HIV disease, even though important details remain to be elucidated. However, a complete understanding of the pathogenesis of a disease is not a prerequisite to knowing its cause. Most infectious agents have been associated with the disease they cause long before their pathogenic mechanisms have been discovered. Because research in pathogenesis is difficult when precise animal models are unavailable, the disease-causing mechanisms in many diseases, including tuberculosis and hepatitis B, are poorly understood. The critics' reasoning would lead to the conclusion that M. tuberculosis is not the cause of tuberculosis or that hepatitis B virus is not a cause of liver disease (Evans. Yale J Biol Med 1982;55:193).

MYTH: AZT and other antiretroviral drugs, not HIV, cause AIDS.

FACT: The vast majority of people with AIDS never received antiretroviral drugs, including those in developed countries prior to the licensure of AZT in 1987, and people in developing countries today where very few individuals have access to these medications (UNAIDS, 2000).

As with medications for any serious diseases, antiretroviral drugs can have toxic side effects. However, there is no evidence that antiretroviral drugs cause the severe immunosuppression that typifies AIDS, and abundant evidence that antiretroviral therapy, when used according to established guidelines, can improve the length and quality of life of HIV-infected individuals (Guidelines for the Use of Antiretroviral Agents in HIV-Infected Adults and Adolescents, 2000).

In the 1980s, clinical trials enrolling patients with AIDS found that AZT given as single-drug therapy conferred a modest (and short-lived) survival advantage compared to placebo. Among HIV-infected patients who had not yet developed AIDS, placebo-controlled trials found that AZT given as single-drug therapy delayed, for a year or two, the onset of AIDS-related illnesses. Significantly, long-term follow-up of these trials did not show a prolonged benefit of AZT, but also never indicated that the drug increased disease progression or mortality. The lack of excess AIDS cases and death in the AZT arms of these placebo-controlled trials effectively counters the argument that AZT causes AIDS (NIAID, 1995).

Subsequent clinical trials found that patients receiving two-drug combinations had up to 50 percent increases in time to progression to AIDS and in survival when compared to people receiving single-drug therapy. In more recent years, three-drug combination therapies have produced another 50 percent to 80 percent improvements in progression to AIDS and in survival when compared to two-drug regimens in clinical trials (Deeks, Volberding, 1999). Use of potent anti-HIV combination therapies has contributed to dramatic reductions in the incidence of AIDS and AIDS-related deaths in populations where these drugs are widely available, an effect which clearly would not be seen if antiretroviral drugs caused AIDS.

MYTH: Behavioral factors such as recreational drug use and multiple sexual partners account for AIDS.

FACT: The proposed behavioral causes of AIDS, such as multiple sexual partners and long-term recreational drug use, have existed for many years. The epidemic of AIDS, characterized by the occurrence of formerly rare opportunistic infections such as Pneumocystis carinii pneumonia (PCP) did not occur in the United States until a previously unknown human retrovirus – HIV – spread through certain communities (NIAID, 1995a; NIAID, 1995b).

Compelling evidence against the hypothesis that behavioral factors cause AIDS comes from recent studies that have followed cohorts of homosexual men for long periods of time and found that only HIV-seropositive men develop AIDS.

For example, in a prospectively studied cohort in Vancouver , 715 homosexual men were followed for a median of 8.6 years. Among 365 HIV-positive individuals, 136 developed AIDS. No AIDS-defining illnesses occurred among 350 seronegative men despite the fact that these men reported appreciable use of inhalable nitrites ("poppers") and other recreational drugs, and frequent receptive anal intercourse (Schechter et al. Lancet 1993;341:658).

Other studies show that among homosexual men and injection-drug users, the specific immune deficit that leads to AIDS – a progressive and sustained loss of CD4+ T cells – is extremely rare in the absence of other immunosuppressive conditions. For example, in the Multicenter AIDS Cohort Study, more than 22,000 T-cell determinations in 2,713 HIV-seronegative homosexual men revealed only one individual with a CD4+ T-cell count persistently lower than 300 cells/mm 3 of blood, and this individual was receiving immunosuppressive therapy (Vermund et al. NEJM 1993;328:442).

In a survey of 229 HIV-seronegative injection-drug users in New York City , mean CD4+ T-cell counts of the group were consistently more than 1000 cells/mm 3 of blood. Only two individuals had two CD4+ T-cell measurements of less than 300/mm 3 of blood, one of whom died with cardiac disease and non-Hodgkin's lymphoma listed as the cause of death (Des Jarlais et al. J Acquir Immune Defic Syndr 1993;6:820).

MYTH: AIDS among transfusion recipients is due to underlying diseases that necessitated the transfusion, rather than to HIV.

FACT: This notion is contradicted by a report by the Transfusion Safety Study Group (TSSG), which compared HIV-negative and HIV-positive blood recipients who had been given transfusions for similar diseases. Approximately 3 years after the transfusion, the mean CD4+ T-cell count in 64 HIV-negative recipients was 850/mm 3 of blood, while 111 HIV-seropositive individuals had average CD4+ T-cell counts of 375/mm 3 of blood. By 1993, there were 37 cases of AIDS in the HIV-infected group, but not a single AIDS-defining illness in the HIV-seronegative transfusion recipients (et al. Ann Intern Med 1990;113:733; Cohen. Science 1994;266:1645).

MYTH: High usage of clotting factor concentrate, not HIV, leads to CD4+ T-cell depletion and AIDS in hemophiliacs.

FACT: This view is contradicted by many studies. For example, among HIV-seronegative patients with hemophilia A enrolled in the Transfusion Safety Study, no significant differences in CD4+ T-cell counts were noted between 79 patients with no or minimal factor treatment and 52 with the largest amount of lifetime treatments. Patients in both groups had CD4+ T cell-counts within the normal range (Hasset et al. Blood 1993;82:1351). In another report from the Transfusion Safety Study, no instances of AIDS-defining illnesses were seen among 402 HIV-seronegative hemophiliacs who had received factor therapy (Aledort et al. NEJM 1993;328:1128).

In a cohort in the United Kingdom , researchers matched 17 HIV-seropositive hemophiliacs with 17 HIV-seronegative hemophiliacs with regard to clotting factor concentrate usage over a ten-year period. During this time, 16 AIDS-defining clinical events occurred in 9 patients, all of whom were HIV-seropositive. No AIDS-defining illnesses occurred among the HIV-negative patients. In each pair, the mean CD4+ T cell count during follow-up was, on average, 500 cells/mm 3 lower in the HIV-seropositive patient (abin< et al. BMJ 1996;312:207).

Among HIV-infected hemophiliacs, Transfusion Safety Study investigators found that neither the purity nor the amount of Factor VIII therapy had a deleterious effect on CD4+ T cell counts (Gjerset et al., Blood 1994;84:1666). Similarly, th Multicenter Hemophilia Cohort Study found no association between the cumulative dose of plasma concentrate and incidence of AIDS among HIV-infected hemophiliacs. MYTH: The distribution of AIDS cases casts doubt on HIV as the cause. Viruses are not gender-specific, yet only a small proportion of AIDS cases are among women.

FACT: The distribution of AIDS cases, whether in the United States or elsewhere in the world, invariably mirrors the prevalence of HIV in a population. In the United States , HIV first appeared in populations of homosexual men and injection-drug users, a majority of whom are male. Because HIV is spread primarily through sex or by the exchange of HIV-contaminated needles during injection-drug use, it is not surprising that a majority of U.S. AIDS cases have occurred in men (U.S. Census Bureau, 1999; UNAIDS, 2000).

Increasingly, however, women in the United States are becoming HIV-infected, usually through the exchange of HIV-contaminated needles or sex with an HIV-infected male. The CDC estimates that 30 percent of new HIV infections in the United States in 1998 were in women. As the number of HIV-infected women has risen, so too has the number of female AIDS patients in the United States . Approximately 23 percent of U.S. adult/adolescent AIDS cases reported to the CDC in 1998 were among women. In 1998, AIDS was the fifth leading cause of death among women aged 25 to 44 in the United States, and the third leading cause of death among African-American women in that age group (NIAID Fact Sheet: HIV/AIDS Statistics).

In Africa, HIV was first recognized in sexually active heterosexuals, and AIDS cases in Africa have occurred at least as frequently in women as in men. Overall, the worldwide distribution of HIV infection and AIDS between men and women is approximately 1 to 1 (U.S. Census Bureau, 1999; UNAIDS, 2000).

MYTH: HIV cannot be the cause of AIDS because the body develops a vigorous antibody response to the virus.

FACT: This reasoning ignores numerous examples of viruses other than HIV that can be pathogenic after evidence of immunity appears. Measles virus may persist for years in brain cells, eventually causing a chronic neurologic disease despite the presence of antibodies. Viruses such as cytomegalovirus, herpes simplex and varicella zoster may be activated after years of latency even in the presence of abundant antibodies. In animals, viral relatives of HIV with long and variable latency periods, such as visna virus in sheep, cause central nervous system damage even after the production of antibodies (NIAID, 1995).

Also, HIV is well recognized as being able to mutate to avoid the ongoing immune response of the host (Levy. Microbiol Rev 1993;57:183).

MYTH: Only a small number of CD4+ T cells are infected by HIV, not enough to damage the immune system.

FACT: New techniques such as the polymerase chain reaction (PCR) have enabled scientists to demonstrate that a much larger proportion of CD4+ T cells are infected than previously realized, particularly in lymphoid tissues. Macrophages and other cell types are also infected with HIV and serve as reservoirs for the virus. Although the fraction of CD4+ T cells that is infected with HIV at any given time is never extremely high (only a small subset of activated cells serve as ideal targets of infection), several groups have shown that rapid cycles of death of infected cells and infection of new target cells occur throughout the course of disease (Richman J Clin Invest 2000;105:565).

MYTH: HIV is not the cause of AIDS because many individuals with HIV have not developed AIDS.

FACT: HIV disease has a prolonged and variable course. The median period of time between infection with HIV and the onset of clinically apparent disease is approximately 10 years in industrialized countries, according to prospective studies of homosexual men in which dates of seroconversion are known. Similar estimates of asymptomatic periods have been made for HIV-infected blood-transfusion recipients, injection-drug users and adult hemophiliacs (Alcabes et al. Epidemiol Rev 1993;15:303).

As with many diseases, a number of factors can influence the course of HIV disease. Factors such as age or genetic differences between individuals, the level of virulence of the individual strain of virus, as well as exogenous influences such as co-infection with other microbes may determine the rate and severity of HIV disease expression. Similarly, some people infected with hepatitis B, for example, show no symptoms or only jaundice and clear their infection, while others suffer disease ranging from chronic liver inflammation to cirrhosis and hepatocellular carcinoma. Co-factors probably also determine why some smokers develop lung cancer while others do not.

MYTH: Some people have many symptoms associated with AIDS but do not have HIV infection.

FACT: Most AIDS symptoms result from the development of opportunistic infections and cancers associated with severe immunosuppression secondary to HIV.

However, immunosuppression has many other potential causes. Individuals who take glucocorticoids and/or immunosuppressive drugs to prevent transplant rejection or for autoimmune diseases can have increased susceptibility to unusual infections, as do individuals with certain genetic conditions, severe malnutrition and certain kinds of cancers. There is no evidence suggesting that the numbers of such cases have risen, while abundant epidemiologic evidence shows a staggering rise in cases of immunosuppression among individuals who share one characteristic: HIV infection.

MYTH: The spectrum of AIDS-related infections seen in different populations proves that AIDS is actually many diseases not caused by HIV.

FACT: The diseases associated with AIDS, such as PCP and Mycobacterium avium complex (MAC), are not caused by HIV but rather result from the immunosuppression caused by HIV disease. As the immune system of an HIV-infected individual weakens, he or she becomes susceptible to the particular viral, fungal and bacterial infections common in the community. For example, HIV-infected people in certain midwestern and mid-Atlantic regions are much more likely than people in New York City to develop histoplasmosis, which is caused by a fungus. A person in Africa is exposed to different pathogens than is an individual in an American city. Children may be exposed to different infectious agents than adults.