department of health and human services Centers for Disease Control and Prevention Poliovirus Infections in Four Unvaccinated Children —

Health (MDH) identified poliovirus type 1 in an unvacci-nated, immunocompromised infant girl aged 7 months (the index patient) in an Amish community whose members pre-dominantly were unvaccinated for polio. The patient has no paralysis; the source of the patient’s infection is unknown. Subsequently, poliovirus infections in three other children within the index patient’s community have been documented. This report summarizes the ongoing investigation, provides information regarding poliovirus exposure risks and preven-tion measures in the United States, and offers recommenda-tions to state health departments and clinicians. Index Case Summary The index patient was first admitted to a community hos-pital in central Minnesota for pneumonia in July 2005. Since August 22, this infant has been hospitalized continuously at three additional hospitals with failure to thrive, diarrhea, and recurrent infections. The infant was placed in strict isolation, and a diagnosis of severe combined immunodeficiency (SCID) was made on September 15. The infant is being clinically managed with intravenous immunoglobulin therapy and is being evaluated for bone marrow transplantation. Laboratory Investigation An enterovirus isolate from a stool specimen obtained on August 27, 2005, tested positive for a type 1 poliovirus at the MDH laboratory. Partial sequencing of the virus capsid pro-tein coding region (VP1) of the poliovirus genome at the MDH laboratory identified it as a vaccine-derived poliovirus (VDPV). VDPVs are poliovirus strains derived from one of the three Sabin poliovirus strains in oral polio vaccine (OPV) that have>1 % difference in nucleotide sequence from the prototype vaccine virus (1). Additional sequencing of the en-tire poliovirus genome at the CDC polio laboratory confirmed that this strain was a VDPV, with 2.3 % divergence in the VP1 region from the parent Sabin type 1 strain. The viral genome demonstrates no recombination with other poliovi-ruses or species C enteroviruses. Prospective serial stool samples from the infant are being tested to monitor ongoing infection and further mutations in the virus