Objectives: To examine the prevalence of polyomavirus SV40 infections in Kazakhstan, a central Asian country known to have used potentially contaminated SV40 poliovaccines before 1962.
Methods: Cross-sectional study of 307 healthy volunteers from two ethnic groups (Kazakhs and Russians) in Almaty, Kazakhstan, from May through August 1999 using a specific SV40 plaque-reduction neutralization assay.
Results: Of the 307 volunteers enrolled in the study, 154 were Kazakhs and 153 were Russians. The overall prevalence of SV40 antibodies was 4.9%, and there was no significant difference between the ethnic groups (p = 0.7) or between males and females. The median SV40 neutralizing antibody titers in Kazakhs and Russians were 1:40 (range 1:10-1:500) and 1:20 (range 1:10-1:500), respectively. The median ages of SV40-infected Kazakhs and Russians were not different (42 vs. 24 years; p = 0.1), although there was a trend for increased seropositivity among older Kazakhs. There was no difference in SV40 positivity between those whose childhoods were spent in rural or in urban areas (p = 0.4). Importantly, 60% (9/15) of the subjects seropositive for SV40 were born from 1969 to 1980s, when poliovaccines were free from SV40.
Conclusions: This study showed evidence of polyomavirus SV40 infections in Kazakhstan, not only among individuals potentially exposed to contaminated poliovaccines, but in younger people not exposed to such vaccines. As increasing evidence indicates an association of SV40 with selected types of human malignancies, prospective studies are needed to examine the risk of SV40 infection with the development of neoplasias.