Abstract
Summary Primary tissue cultures prepared from Aedes aegypti embryos were inoculated with Eastern equine encephalomyelitis, Semliki Forest, and West Nile viruses. The viruses multiplied in this in vitro system and were present in the cultures for periods as long as 60 days after infection. The growth process for the three viruses proceeds differently: WN virus is the slowest growing, EEE is intermediate, and the SF virus grows fastest. Cultures infected with WN virus did not show morphologic changes, whereas those inoculated with EEE or SF viruses occasionally displayed cellular alterations. There is no evidence that these cellular alterations can be attributed to virus infection. The presence of EEE virus in cultures was also verified by the hemagglutination test, but no hemagglutinin was detected in cultures infected with WN and SF viruses.