"Two new retroviruses - the type of virus which causes AIDS - have jumped from non-human primates to people, a new study reveals.
The study of blood samples from nearly a thousand bushmeat hunters or handlers in Cameroon showed that at least six viruses had crossed from monkeys
to the people who were exposed to freshly caught bushmeat. And two of these viruses have never been seen before in humans.
The newly discovered human T-cell lymphotropic virus 3 (HTLV-3) and HTLV-4 are closely related to the known viruses, HTLV-1 and HTLV-2. These are
implicated in cancers like leukaemia and can cause inflammatory or neurological diseases.
Retroviruses such as HTLV or HIV insert their genetic material into a host cell's DNA. The emergence of HIV is widely blamed on a primate retrovirus,
SIV, jumping to humans. Previously, it was thought that the emergence of these viruses was limited by the rarity of successful cross-species
But the identification of two entirely new human retroviruses from one study, along with a previous discovery by the same group that simian foamy
viruses can jump from monkeys to humans, may be ominous.
"What's increasingly clear is that the hunting and butchering of non-human primates is associated with the transmission of retroviruses to humans,"
says Nathan Wolfe, at the Johns Hopkins Bloomberg School of Public Health in Baltimore, US, who led the study.
He says the new results suggest the team's previous find of simian foamy viruses in bushmeat hunters was "not just a fluke". In the blood-screening
study, 13 out of 930 people were found to be infected with simian retroviruses, and two with the new human strains.
The new findings are no surprise, agrees Martine Peeters at the retrovirus laboratory of the Institute of Research for Development in Montpelier,
France. She and her colleagues, along with other groups, had described simian TLV-3 in primates in Cameroon in 2004 so the discovery of a human
equivalent is not unexpected. Now scientists will look for the simian equivalent of HTLV-4.
HTLV-1 and -2 are not very pathogenic says Peeters, but about 1% of those infected may go on to develop leukaemia."
How many months or years will it take these new virus to infect the planet? Are these the "plagues" foretold in the book of Revelations?