Strain characterization studies of poliovirus type I isolates from poliomyelitis cases in the United States in 1979.

In 1979 there was a small outbreak of poliomyelitis among non-immunized Amish individuals in the United States. Epidemiological evidence linked these cases to those in Canada in 1978 which themselves were related to cases in the Netherlands in 1978. Poliovirus type 1 was found to be the cause both in the US and in the other countries. Strain characterization tests were carried out on virus isolates from all three outbreaks. All the type 1 strains were non-vaccine-like both with the absorbed strain specific antisera and with the modified Wecker test. However, the latter as well as the rct test used to characterize these strains are obviously not very discriminating marker tests. The oligonucleotide mapping procedure appears to be a much more definitive approach to recognizing relationships between polioviruses. The various marker tests provided laboratory data in support of the epidemiological evidence that the poliovirus type 1 spread from Holland to Canada in 1978 and from there to the US in 1979.