WASHINGTON (Reuters) - Two new retroviruses never before seen in humans have turned up among people who regularly hunt monkeys in Cameroon, researchers reported on Friday. Like the AIDS (news - web sites) virus, these viruses insert their genetic material directly into cells and perhaps even into a person's or animal's chromosomes. Closely related versions of the viruses cause leukemia, inflammatory and neurological diseases. The two new viruses are called human T-lymphotropic virus types 3 and 4 or HTLV-3 and HTLV-4. They are closely related to two known viruses called HTLV-1 and HTLV-2, which experts believe were transmitted to people,...