The AIDS virus may have lost strength, at least in terms of how well it multiplies. Using HIV-1 from untreated patients, molecular virologists tested samples from 1986 to 1989 and from 2002 to 2003. After dosing human blood and immune cells with the viruses, they found the older HIV replicated significantly better than more recent samples and also appeared less sensitive to anti-HIV drugs. HIV-1, the most common strain of the virus worldwide, may be adapting to humans as it passes from person to person and becoming less efficient at multiplying to guarantee its continued survival in the host. The virus could fade into a nonlethal form “in 20, 200 or 2,000 years; there is no way to tell without further studies,” says Eric Arts of Case Western Reserve University, member of a team that includes researchers from the Institute of Tropical Medicine in Antwerp. The results appear in the October 14 AIDS.