WASHINGTON D.C.: Two of four strains of the virus that can cause AIDS come from gorillas in southwestern Cameroon, an international team of scientists reported in studies published on Monday (Tuesday in Manila) in the United States. The new information means that researchers now know the origins of all strains of the HIV virus that occur in people. HIV (HIV-1) has at least four strains. Known as Groups M, N, O and P, each one had its own origin—from ape to man, on at least four separate occasions. Groups M and N were known to have come from chimpanzees in Cameroon. But until now the origin of the O and P strains had been unknown.