Learn About HIV / AIDS

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Myths and Facts about HIV

Why do some people make statements that HIV does not cause AIDS?

The epidemic of HIV and AIDS has attracted much attention both within and outside the medical and scientific communities. Much of this attention comes from the many social issues related to this disease such as sexuality, drug use, and poverty. Although the scientific evidence is overwhelming and compelling that HIV is the cause of AIDS, the disease process is still not completely understood. This incomplete understanding has led some persons to make statements that AIDS is not caused by an infectious agent or is caused by a virus that is not HIV. This is not only misleading, but may have dangerous consequences. Before the discovery of HIV, evidence from epidemiologic studies involving tracing of patients' sex partners and cases occurring in persons receiving transfusions of blood or blood clotting products had clearly indicated that the underlying cause of the condition was an infectious agent. Infection with HIV has been the sole common factor shared by AIDS cases throughout the world among men who have sex with men, transfusion recipients, persons with hemophilia, sex partners of infected persons, children born to infected women, and occupationally exposed health care workers.

The conclusion after more than 20 years of scientific research is that people, if exposed to HIV through sexual contact or injecting drug use for example, may become infected with HIV. If they become infected, most will eventually develop AIDS.

ANSWERING THE SKEPTICS:
RESPONSES TO ARGUMENTS THAT HIV DOES NOT CAUSE AIDS

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 (Jackson et al. J Clin Microbiol 1990;28:16; Busch et al. NEJM 1991;325:1; Silvester et al. J Acquir Immune Defic Syndr Hum Retrovirol 1995;8:411; Urassa et al. J Clin Virol 1999;14:25; Nkengasong et al. AIDS 1999;13:109; Samdal et al. Clin Diagn Virol 1996;7:55.

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.

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. 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 (Figure 1; CDC. HIV AIDS Surveillance Report 1999;11[2]:1; Palella et al. NEJM 1998;338:853; Mocroft et al. Lancet 1998;352:1725; Mocroft et al. Lancet 2000;356:291; Vittinghoff et al. J Infect Dis 1999;179:717; Detels et al. JAMA 1998;280:1497; de Martino et al. JAMA 2000;284:190; CASCADE Collaboration. Lancet 2000;355:1158; Hogg et al. CMAJ 1999;160:659; Schwarcz et al. Am J Epidemiol 2000;152:178; Kaplan et al. Clin Infect Dis 2000;30:S5; McNaghten et al. AIDS 1999;13:1687).

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/mm3 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/mm3 of blood. Only two individuals had two CD4+ T-cell measurements of less than 300/mm3 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).

Data source: Centers for Disease Control & Prevention Website