SV40: Simian virus 40, a polyomavirus found in simians (nonhuman primates), SV40 has no relationship to the human immunodeficiency virus (HIV) or to the simian immunodeficiency virus (SIV).
Some lots of polio vaccines in the 1960s were discovered to contain SV40. It was found in the inactivated (Salk) polio vaccine and some experimental lots of oral (Sabin) polio vaccine. The vaccine in those lots had been manufactured in kidney cells from simians (monkeys) that harbored SV40. The control methods used before this time did not identify this adventitious agent. The formalin inactivation process used to kill the poliovirus was found not to inactivate the SV40 completely. Since 1961, manufacturers have been required to test for SV 40. A few years later, the source of monkeys used for production was changed to species that do not harbor SV40.
There is limited evidence that SV40 can infect humans, but there is no evidence it causes human health problems and there is specifically no evidence that exposure to SV40 is associated with cancer in humans.