Monkey Virus Transmitted To Humans NEW YORK (Reuters) -- Retroviruses such as HIV are thought to have originated in monkeys and later jumped the "species barrier" to infect humans. Now scientists reporting in the journal Nature Medicine say another monkey-borne retrovirus, known as simian foamy virus (SFV), has been found in the bloodstreams of four animal researchers. "Our findings represent the first known human infections with baboon SFV and confirms human susceptibility," say researchers led by scientists at the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia. They stress that all human foamy virus infections have so far remained asymptomatic, and have not been transmitted between humans through either casual or sexual contact. After it became clear that HIV and another retrovirus, called human T cell leukemia/lymphotropic virus (HTLV), probably originated in primates before infecting humans, scientists have been on the alert for similar transmissions. The CDC-led team tested blood samples of 2,018 researchers at 13 US and Canadian scientific institutions, most of whom come into close regular contact with primates of various species for years at a time. A subset of 231 of these workers were tested for infection with SFV. Four (1.8%) of these workers were found to carry the SFV virus, although they showed no signs of disease. "All reported a history of injuries," the researchers say, including serious bites from chimpanzees, baboons or African green monkeys, some occurring as far back as 20 years ago. However, the researchers report no subsequent (HIV-like) human-to-human transmission of these viruses. They believe the virus has so far remained unable to fully "adapt to the human host and become more transmissible." Although SFV is readily found in monkey saliva, the saliva of each of the four infected humans has so far tested negative for the organism. And all blood samples from the spouses of the infected workers "were negative (for SFV)... despite documented (sexual and casual) exposure to infected partners for 9, 15 and 19 years," according to the study authors. Still, the CDC-led team believe there is a potential for SFV transmission (and further adaptation), especially through donated blood. They say they are "counseling all SFV-infected persons to refrain from blood and tissue donation until risks of transmission by blood are defined." In an accompanying editorial, Dr. Robin Weiss of the Institute of Cancer Research in London, England, points out that animal-to-human transplantation (xenotransplantation) may also provide opportunities of interspecies viral transmissions. "It is the fear of triggering a new human epidemic... that has led to a call for a moratorium on xenotransplantation of animal tissues into humans," Weiss said. SOURCE: Nature Medicine (1998;4(4):391-392, 403-407)
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