Poliomyelitis--United States, Canada.

As of May 22, an additional case of polio caused by type 1 poliovirus has been reported in Pennsylvania, bringing to 4 the total number of such cases this year. Two other states have reported suspected cases. Three of the confirmed and both suspected cases are in Amish residents. In addition, Ontario, Canada, has confirmed a case of paralytic poliomyelitis (type 1 virus) in an Amish woman.