Protocol for the investigation of acute flaccid paralysis and suspected paralytic poliomyelitis.

Paralytic poliomyelitis has been nationally notifiable in Canada since 1924. The last case of indigenous wild paralytic poliomyelitis in Canada occurred in 1977, and Canada, along with the rest of the American Region, was formally certified as polio-free by the International Commission for the Certification of Poliomyelitis Eradication in September 1994(1). Despite the elimination of indigenous wild poliovirus transmission, however, it remains essential that surveillance be maintained until global eradication is achieved because of the risk of wild virus importation from endemic regions. Paralytic poliomyelitis cases resulting from wild virus importations were reported in Canada in 1978 and 1988(2,3). Two other recognized instances of wild virus importation in 1993 and 1996 were not associated with paralytic (or nonparalytic) illness(4,5). The sensitivity of the previous passive surveillance system for poliomyelitis in Canada has been limited in recent years by the low index of diagnostic suspicion and the false sense of security that often occurs when a disease becomes rare. Thus, active surveillance of acute flaccid paralysis (AFP) in children < 15 years old was initiated in 1991 to screen for potential cases of poliomyelitis. AFP surveillance formed a critical component of the polio eradication campaign in the Americas and continues to play an essential role in the World Health Organization global polio eradication campaign(6). By using an expected annual background incidence of approximately one case of AFP per 100,000 in the population < 15 years old in the absence of wild poliovirus transmission(1), AFP surveillance serves as a good indicator of the level of monitoring for potential cases of paralytic poliomyelitis from imported virus into polio-free regions. Further, with proper laboratory and neurologic investigation of cases, AFP surveillance greatly improves the sensitivity for rapid detection of paralytic poliomyelitis. AFP surveillance in Canada is being implemented through a collaborative effort between the Laboratory Centre for Disease Control (LCDC) and the Canadian Paediatric Surveillance Program. Surveillance is based on reporting through the Immunization Monitoring Program, Active system, a network of 11 pediatric tertiary-care centres across the country, as well as reporting by pediatricians. All suspected cases of paralytic poliomyelitis reported to LCDC are evaluated by the national Working Group on Polio Eradication to rule out or confirm the diagnosis.