The rate at which HIV replicates might be slowing, suggesting that the virus might have become weaker since the 1980s, according to a study published online on Thursday in the journal AIDS, the Long Island Newsday reports. Researchers from the Prince Leopold Institute of Tropical Medicine in Antwerp, Belgium, and Case Western Reserve University in Cleveland compared 12 HIV-1 samples collected from patients between 1986 and 1989 to 12 samples of the virus collected between 2002 and 2003. Although the samples in the 1980s were taken from different patients than the 2002-2003 samples, the viruses were closely matched genetically (Ricks, Long Island Newsday, 9/30). The researchers allowed the 12 genetically matched viral pairs to replicate in a medium of white blood cells in petri dishes. In nine of the 12 pairs, the older virus replicated more quickly than the newer samples, according to the study (Alexander/Tannenbaum, Bloomberg/Arkansas Democrat-Gazette, 9/30). The researchers concluded that the findings suggest that the virus's "replicative fitness" in humans might have decreased since the beginning of the pandemic (Birmingham Post, 9/30). Study author Eric Artz said, "[W]e did find a pretty striking observation in that the viruses from the 2000s are much weaker than the viruses from the 80s," adding that he believes HIV could stop causing death in humans within another 50 to 60 years based on the findings (BBC News, 9/29). The researchers theorized that the virus might be weakening as a way to survive longer in the host (Long Island Newsday, 9/30).

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Some AIDS experts warned that the findings do not suggest that HIV is less contagious or deadly. "The bottom line is that HIV is still dangerous," Carl Dieffenbach, head of the basic science program in the Division of AIDS at the National Institute of Allergy and Infectious Diseases, said, adding, "If it is attenuating, it is not doing it enough to make a difference in outcomes." Marco Vitoria, an AIDS expert at the World Health Organization, criticized the study for being "very small" and said that "attenuation isn't new in the natural history of many other infectious diseases and is a very slow process, to be measured not in years but in generations." He added that diseases such as tuberculosis, syphilis and smallpox were more aggressive thousands of years ago but noted that they remain lethal contagions (Bloomberg/Arkansas Democrat-Gazette, 9/30). Gary Leonardi, chief of virology at Nassau University Medical Center in East Meadow, N.Y., said that drug-resistant strains of HIV tend to be more aggressive. "When you expose the virus to (drugs) from the point of evolution, you are telling the virus to mutate or die," he said, adding, "What we've mostly seen is that the virus has chosen to mutate. It's what is called survival of the fittest." In addition, Charles Gonzalez, an infectious disease expert at New York University in New York City, questioned the researchers' ability to effectively culture reliable samples in the 1980s. "I know that because I was doing sampling then, and I am doing sampling now" (Long Island Newsday, 9/30).

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