Researchers have long assumed that SIVcpz, the chimpanzee virus that infected humans and triggered the AIDS epidemic, caused no harm to the apes. But new data presented here today at the 16th Conference on Retroviruses and Opportunistic Infections reveal that wild chimps infected with SIVcpz are more likely to die than uninfected chimps. The animals also show AIDS-like damage to their immune systems. The finding raises the possibility that chimps, too, are suffering from an AIDS epidemic.