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MACS and WIHS Studies Provide Overwhelming Evidence That HIV Causes AIDS

Commentary by the Principal Investigators of the Multicenter AIDS Cohort Study (MACS) and the Women's Interagency HIV Study (WIHS): Kathryn Anastos, M.D.; Mardge Cohen, M.D.; Roger Detels, M.D.; Stephen Gange, Ph.D.; Ruth Greenblatt, M.D.; Lisa Jacobson, Sc.D.; Alexandra Levine, M.D.; Joseph Margolick, M.D., Ph.D.; Howard Minkoff, M.D.; Alvaro Muñoz, Ph.D.; John Phair, M.D.; Charles Rinaldo, Ph.D.; Mary Young, M.D., and by Paolo Miotti, M.D., M.P.H, Chief of the Epidemiology Branch, Division of AIDS, NIAID.

Recent discussions questioning whether the human immunodeficiency virus (HIV) causes the acquired immunodeficiency syndrome (AIDS) reopen an unnecessary debate in the face of overwhelming scientific evidence, potentially delaying desperately needed interventions and thus prolonging a tragedy that threatens the entire world. As the investigators of two large studies conducted in several cities across the United States, we would like to add our voices, and our data, to those who see this debate as a diversion of vital resources at a time when diversion is a fatal mistake. The data from the Multicenter AIDS Study (MACS) and the Women's Interagency HIV Study (WIHS) have demonstrated convincingly that HIV is the cause of AIDS.

The MACS has been following 5,622 men since 1984; the WIHS has observed 2,628 women since 1994. In both studies, participants are seen every six months. At these visits, extensive tests are conducted to establish the health of the participant (including the array of medications taken), to determine whether they have AIDS, and to evaluate the immune system and HIV infection. People with and without HIV are studied. For example, in the MACS, approximately half the men never tested positive for HIV infection. When the length of time these participants have been studied is combined with the number of participants in the two studies, we can be confident in the conclusions, because they are based on thousands of observations over more than sixteen years.

The inescapable conclusion from the more than 750 scientific reports produced by our studies is that HIV is the cause of AIDS. The evidence to support this conclusion is powerful:

  1. The presence of HIV infection is the only factor that is strongly and consistently associated with the conditions that define AIDS;
  2. The higher the amount of HIV in the blood, the greater the risk of developing AIDS (Annals of Internal Medicine 1997; Journal of Acquired Immune Deficiency Syndromes 1999);
  3. When therapies that prevent HIV from replicating were used to drastically reduce the amount of HIV in a patient's blood, there was also a dramatic and unprecedented decrease in the incidence of AIDS and death (Journal of the American Medical Association 1998); and
  4. Even in individuals infected with the virus that causes Kaposi's sarcoma, Kaposi's is extremely unlikely to occur without the immunosuppression caused by HIV infection (Journal of Infectious Diseases 2000).

In our studies, the risk of developing an AIDS-like illness in persons who did not have HIV was 1,100 times less than the risk in persons with HIV; these overwhelming odds provide a clarity of association that is unusual in medical research. Full clinical AIDS (seen in 1,715 MACS participants and 1,075 WIHS participants) always occurred in participants who had previously tested positive for HIV. HIV infects immune cells called CD4-bearing T-helper cells, or more simply, CD4 cells.

A low level of CD4 cells is a hallmark of HIV infection and predicts both illness and death. From over 40,000 samples collected in uninfected MACS and WIHS participants, only sixteen samples from six HIV-negative participants had CD4 cell counts that were low enough to be like those found in AIDS patients (less than 200 CD4 cells per cubic millimeter of blood).

The most stunning evidence is seen in the effects of new drugs for the control of the HIV virus. Persons with debilitating AIDS symptoms have seen marked improvements in their health once the virus was controlled bydrugs. These case studies have been confirmed and expanded by the MACS and WIHS, where maintenance of health and improvement in health have been seen in participants as long as the HIV virus remains controlled.

Disputing the overwhelming evidence that HIV causes AIDS is not only unscientific, but also inexcusably derails the only known approaches that can stop the terrible pandemic of AIDS. While the best approaches to improving health in settings with limited funded and substantial epidemics can be debated, the results of the studies conducted in the last sixteen years are indisputable: HIV causes AIDS.

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Last Updated September 25, 2005