What Causes AIDS?

The debate continues

From the December 1994 issue

(Page 3 of 7)

If the authors of this article truly believe that there is an epidemic of deaths from sustained immune deficiency that can not be explained by HIV or other known causes, I urge them to avoid the entrenched HIV=AIDS hypothesis by reporting these cases to the CDC as a new disease, rather than attempting to link them to AIDS.

George Fergus
Schaumburg, IL

Thomas, Mullis, and Johnson state that "chimps have repeatedly been infected with HIV, but none of them have developed HIV." True enough, and none ever will. Chimps are not susceptible to HIV because that virus targets the human, not simian, genome. But chimps infected with the SIV (simian immunodeficiency virus, a virus genetically similar but not identical to HIV) do develop suppressed immune systems and the symptoms of AIDS. It is inexplicable that these writers do not recognize that a chimp's failure to contract AIDS from HIV no more addresses the consequences of HIV infection in humans than does the human failure to contract feline leukemia virus indicate that cats cannot contract leukemia either.

This impressive display of epidemiological ignorance casts doubt on their ability to interpret evidence wisely, but there's more.

They say the virus is generally not detectable in people with advanced AIDS; a large body of literature exists confirming that the virus is present and detectable during all stages of the disease. They claim HIV is a simple retrovirus that is not capable of the sophisticated behavior it apparently displays; epidemiologists have described HIV as a complex virus whose full genome is not yet understood.

Thomas, Mullis, and Johnson imply that Warner C. Green in an article in the September 1993 Scientific American acknowledges the supposed tenuous connection between HIV and AIDS. Green does nothing of the sort. In fact, in that article he writes: "I must emphasize that all responsible opinion holds that HIV is indeed the cause of AIDS. A small number of cases of people with immune deficiency who are not infected with HIV received inappropriately widespread publicity last year, which fostered the unsubstantiated notion that there is another cause of AIDS not detected by current blood tests."

The authors also suggest that causality between HIV and AIDS has not been proven; all we have, they say, is a correlation between the two. Science, however, will never be able to "prove" that HIV causes AIDS any more that it can prove that varicella causes chicken pox. Proving a positive is an impossibility (an assertion can only be disproven). All relationships between viral infections and resulting symptoms are ultimately correlational. (With HIV the authors fail to assert that this correlation is strong; virtually everyone infected with HIV develops AIDS-like symptoms within 10 years.)

HIV may not be the cause of AIDS, but the overwhelming body of evidence tells us otherwise. Suggesting, as the authors do, that the government is standing in the way of finding the real cause of AIDS given the amazing lack of evidence for such a statement is irresponsible. The authors should not have made it, and REASON magazine should not have printed it.

Mark W. Nowak
Arlington, VA

The epidemiologic, laboratory, and clinical evidence that HIV is the cause of AIDS is overwhelming. This evidence has been used as a basis for national and international prevention programs and clinical and vaccine trials.

Thomas et al. mix fact with fiction to misinform readers. For example, the authors suggest that AIDS cases are an artifact of the CDC's AIDS surveillance case definition, that there are "thousands of cases of AIDS without HIV," and that "such cases tend to disappear from the official statistics."

The AIDS surveillance case definition was not designed to prove the existence of HIV. However, it provides additional evidence to what epidemiologic and laboratory studies have already told researchers-that HIV causes AIDS. Case definitions of any disease or health condition are basic tools of public health surveillance. They are devised by epidemic investigators in response to clusters or outbreaks of new or unusual health phenomena. The first CDC AIDS surveillance case definition was developed in response to clusters of patients with unexplained opportunistic infections and Kaposi's sarcoma in 1981. Patterns identified from early case reports provided convincing evidence that the new syndrome was caused by an infectious agent. This definition has been expanded three times (in 1985, 1987, and 1993) in response to greatly increased knowledge of the immunopathology and health effects of HIV infection; each expansion served to encompass more persons with symptomatic HIV infection. Thus, far from being an artifact, the CDC's AIDS surveillance case definition is what it was intended to be-a tool to track the many persons in the latter stages of HIV infection.

The authors claimed that there are "thousands of cases of AIDS without HIV." A small percentage of cases reported to CDC have been in patients who have never had an HIV antibody test. The majority of these cases were diagnosed and reported before the first HIV antibody test was licensed in 1985. These cases were diagnosed based on the presence of "indicator" diseases (mainly Pneumocystis carinii pneumonia and Kaposi's sarcoma) that are very rare in immunocompetent persons not infected with HIV. In addition, their supposition that these cases were further defined as idiopathic CD4+ T-lymphocytopenia (ICL) is not true. Investigations show that ICL cases and AIDS cases differ epidemiologically. Thus far, researchers have found that ICL is rare, and that no more than 100 of these cases exist.

AIDS cases do not disappear. Missing or incomplete information that accompanies AIDS cases reported to CDC through state health departments is often updated. Most cases reported without risk information are reclassified as follow-up investigations are completed.

The inevitable conclusions of more than a decade of research are that most people exposed to HIV through sexual contact, injecting drugs, or transfusions are susceptible to HIV infection. Nearly all persons who become infected with HIV will eventually develop AIDS.