Viral Sex

The current worldwide AIDS crisis is about 20 years old, but the disease itself is much older. In fact, AIDS is only the latest chapter in the evolution of the complex retrovirus we call HIV. Where was HIV lurking before it emerged in the early 1980s? There is some evidence that the Westernstrain of HIV arose in Europe as early as 1939. There is even more evidence that HIV is a direct descendant of a virus which has long infected certain African apes and monkeys, a virus called SIV--simian immun