On Jul. 27, 1979, the last cases of wild type 1 poliovirus occurred in the U.S. among unvaccinated Amish persons and members of other religious groups who did not accept vaccination. The source of the outbreak was determined to have been brought over to the U.S. from the Netherlands by members of an unvaccinated religious group.

Fourteen of these cases (all paralytic) occurred in unvaccinated Amish persons; 2 (both nonparalytic) were in unvaccinated non-Amish persons, who lived in or near an Amish area; and 1 case (paralytic) occurred in an Amish infant, who received oral poliovirus vaccine 5 days before becoming ill. In the latter case, the patient had laboratory evidence of recent infection with both type 1 and type 2 poliovirus; the other 16 cases were clearly due to a wild (type 1 poliovirus. These 17 cases have been reported from 4 different states (Pennsylvania, 8 cases; Iowa, 3; Wisconsin, 3; Missouri, 1) and Canada (2). Immunization campaigns for the Amish are continuing; at least half of the nation’s Amish have now received 1 or more doses of oral poliovirus vaccine.

The type 1 poliovirus isolated from the first 1979 poliomyelitis patient (an Amish female from Pennsylvania) showed a resemblance to a wild type 1 strain isolated in Kuwait in 1977. Type 1 strains from cases occurring in the 1978 epidemic in the Netherlands and Canada also showed a resemblance to the Kuwait poliovirus strain.