1 Departments of Pediatrics and Microbiology, State University of New York Upstate Medical Center
An attenuated poliovirus Type III strain (Leon 12a1b) was fed to six members of a summer recreational school program in a small community in the central part of New York. Transmission of this virus occurred to only 3 of 25 family contacts of these six children and to only 1 of 13 close school associates. In addition, five more casual school and neighborhood contacts became infected during the study period. Thus, only 9 of 100 family and school contacts of these school children became infected during a 5-week study period.
The results have been interpreted to suggest that the attenuated poliovirus Type III strain (Leon 12a1b) is less invasive in open populations than the natural polioviruses previously observed. It is likely that the increased prevalence of Coxsackie B2 and B3 infections and perhaps other enteroviruses may have had some effect on the spread of the attenuated polioviruses. However, it seems unlikely that these latter two factors could have explained the striking differences observed.