According to Prof. Shope, the persons indicated with a + all "...worked with 
SFV on a regular basis between 1949 and 1970, usually on an open bench, and 
mostly with mouth pippetting. Many of these persons continued to work with 
SFV after 1970, but under BL 2 and BL 3 conditions. The strain of SFV 
employed was a low-passage descendant of the earliest prototype virus, isolated 
by Smithbum and Haddow, in 1942. 
Other persons tested worked in the Rockefeller Foundation Virus Laboratories or 
its successor organization, the Yale Arbovirus Research Unit, most of them for 
years, in laboratories where Semliki Forest virus research was being conducted. 
They were not, however, personally engaged in this research at the bench level, 
or did not work for very long periods with Semliki Forest virus." 
Prof. Shope noted that all persons exposed to SFV performed experiments with 
animals, as tissue culture studies in the Arbovirus Research Unit did not begin 
until after 1970. 
Only one individual, MC-W, was strongly reactive to SFV; but she had not 
worked with SFV in the Yale Arbovirus Research Unit since her employment at 
Yale two years before. Prof. Shope noted that "MC-W worked with Semliki 
Forest virus for several years in Abidjan and Bangui, then later as the lead 
technical person in the diagnostic unit of the Institut Pasteur, Dakar. She was 
potentially exposed to natural infection in Africa. She has no history of 
encephalitis or other severe illness that might be linked to Semliki Forest virus 
infection." 
Seven other individuals were reactive for SFV. Two (RS and OLW) were 
borderline positive. The other five demonstrate significant reactivity to SFV, but 
because they are more reactive with another member of the Semliki complex of 
viruses, these workers were judged to be infected by the virus giving the highest 
dilution titre. Based on these results, however, one cannot conclusively exclude 
a coincident infection with SFV. 
Institute of Biotechnology, University of Helsinki 
A second survey of laboratory workers exposed to SFV was provided by 
Professor L.Kairiainen (courtesy of Prof. A. Helenius, Yale University). 
According to Prof. Kaarianen, each individual tested had worked with SFV, on 
average, for about five years, under BL2 conditions. This laboratory has studied 
SFV since 1965, handling altogether "at least several grams of virus" with no 
sign of overt infection. All studies with SFV involved tissue culture; none was 
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