HIV is amazingly protean, averaging one alteration of its genetic code every time it infects a new cell, which it does millions of times each day in each patient. The math is dizzying. With tens of millions of people infected globally, HIV is probably changing every letter in its genetic code many times every day.
But HIV can leap ahead of even its swift pace of mutation by "recombination." If a person gets infected with two separate strains, then through a kind of viral sex those strains can mix their genetic material to form a hybrid strain. Through recombination, a virus can instantly and radically transform itself. Several of HIV's subtypes were formed through this process.
photo: Mark Schoofs
Karakoula Bertheloise, shown here with his wife, is a hunter in the Cameroon rainforest. He hunts whatever game he can, including monkeys and apes.
That's a reason to study the origin of HIV. Some researchers envision a science of emerging microbes that could short-circuit viral evolution and protect humans. But for the moment, recombination is a reason to worry about new types of HIV entering human beings: the greater the variety of strains, the greater the chance that they will reshuffle their parts into a more dangerous subtype. "There is genetic engineering going on in nature," says Piot of UNAIDS. "The virus is experimenting with itself."
"The most striking case I have seen in the last six months," says Zekeng, "was a 45-year-old man sent to me from the TB unit. He had chest problems but not TB. He had lost weight. He had KS"an HIV-related cancer"on his ankle. And he had a persistent fever." In short, a classic AIDS case. "Yet herepeatedlytested negative on at least six different screening tests." Twice, Zekeng has sent this man's blood to a state-of-the-art laboratory in Germany, but no virus has been detected. "Is it going to be HIV-3?" asks Zekeng. "I don't know."