Skip Navigation LinksSkip Navigation Links
Centers for Disease Control and Prevention
Safer Healthier People
Blue White
Blue White
bottom curve
CDC Home Search Health Topics A-Z spacer spacer
Blue curve MMWR spacer

Isolation of Wild Poliovirus Type 3 Among Members of a Religious Community Objecting to Vaccination -- Alberta, Canada, 1993

During September 1992-February 1993, 68 cases of poliomyelitis occurred among members of a religious community in the Netherlands (1). Because members of an affiliated religious community in Alberta, Canada, had direct contact (i.e, travel to and from the Netherlands) with members of the affected community, health authorities in Alberta conducted an investigation during January-February 1993 to determine whether this poliovirus had been imported. This report summarizes the results of this investigation (2).

The investigation focused on a small rural community in southern Alberta that reported the only case of poliomyelitis from the province during the last outbreak (11 cases) of poliomyelitis in Canada during 1978 (3,4). The community comprises members of a religious group that generally opposes vaccination.

Wild poliovirus type 3 (PV3) was isolated from stool specimens obtained from 21 (47%) of 45 persons (primarily children). Laboratory investigations conducted by the National Center for Enteroviruses in Halifax, including application of molecular techniques in collaboration with laboratories at CDC, determined that this PV3 was virtually identical with the strain that caused the recent outbreak in the Netherlands.

No cases of paralytic poliomyelitis have been identified in Canada since 1988. Provincial epidemiologists in Canada, in collaboration with the Laboratory Center for Disease Control in Ottawa, have enhanced surveillance for cases of acute flaccid paralysis. In addition, poliovirus vaccine has been offered to members of all unvaccinated communities. Studies are under way to determine whether poliovirus is circulating among unvaccinated communities in British Columbia and Ontario. Adapted from: Canada Communicable Disease Report 1993;19:57-8.

Reported by: Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases; Div of Immunization, National Center for Prevention Svcs, CDC.

Editorial Note

Editorial Note: The findings in this report represent the first documented importation and circulation of any wild poliovirus in the Western Hemisphere since the apparent eradication of wild poliovirus infection in August 1991 (5). No cases of paralytic poliomyelitis have been reported from the affected community in Alberta; however, because the clinical:subclinical case ratio for PV3 infection may be as low as 1:1000 (6 ), wild poliovirus can circulate in a population group for several months before paralytic disease occurs. The last outbreak of poliomyelitis in the United States occurred in 1979 when 10 paralytic cases were reported from four states (Iowa, Missouri, Pennsylvania, and Wisconsin). That outbreak originated in the Netherlands in 1978 when poliovirus type 1 spread from the Netherlands to Canada and then to the United States (3,4,7,8).

In each of these outbreaks, clinical cases of poliomyelitis and asymptomatic infections occurred almost exclusively among religious groups objecting to vaccination. Subgroups of susceptible persons residing within otherwise highly vaccinated general populations can periodically support epidemic transmission of poliomyelitis (3,4,7,8). However, the risk for exposure, infection, and paralytic disease among vaccinated persons in the general population is low. Therefore, persons fully vaccinated with poliovirus vaccine (i.e., three to four doses of vaccine) are not considered at increased risk for poliomyelitis, and special efforts (i.e., additional vaccination) are not recommended.

Because of the risk for importation and spread of poliovirus, all persons aged less than 18 years who are not fully vaccinated should initiate or complete the primary series of poliovirus vaccine according to the recommendations of the Advisory Committee on Immunization Practices (9,10). In addition, special efforts are necessary to increase acceptance rates of vaccination and to provide poliovirus vaccines to unvaccinated or incompletely vaccinated members of religious groups who do not generally accept vaccination. Oral poliovirus vaccine (OPV) is recommended for all unvaccinated persons residing in these communities, including those aged greater than or equal to 18 years, because of its ability to limit community spread if poliovirus is introduced.

Because of the outbreak in the Netherlands and detection of PV3 in Alberta, surveillance of poliomyelitis in the United States has been augmented to include clinical and laboratory investigations of any case of acute paralysis or aseptic meningitis occurring among members of religious groups objecting to vaccination, as well as unvaccinated persons in the general population residing in the vicinity of these religious groups. In addition, studies are under way to document the presence or absence of wild poliovirus in the United States among communities that do not accept vaccination.

The documentation of imported wild poliovirus in Alberta -- following a period of 18 months during which wild poliovirus was absent in the Americas -- demonstrates the potential for reintroduction of poliovirus into areas where poliomyelitis was considered eliminated. Persons belonging to religious communities objecting to vaccination are currently at greatest risk for paralytic poliomyelitis in the United States. Although efforts are ongoing to protect these communities, the effectiveness of previous vaccination efforts in these communities has been limited. Only global eradication of poliomyelitis -- a health goal for the year 2000 adopted by the World Health Assembly in 1988 -- will ensure that poliovirus infection will not cause paralytic disease in the United States or the rest of the world.


  1. CDC. Update: poliomyelitis outbreak -- Netherlands, 1992. MMWR 1992;41:917-9.

  2. Health and Welfare Canada. Preliminary report: wild poliovirus isolated in Alberta, 1993. Canada Communicable Disease Report 1993;19:57-8.

  3. White FMM, Lacey BA, Constance PDA. An outbreak of poliovirus infection in Alberta, 1978. Can J Public Health 1981;72:239-44.

  4. Varughese PV, Carter AO, Acres SE, Furesz J. Eradication of indigenous poliomyelitis in Canada: impact of vaccination strategies. Can J Public Health 1989;80:363-8.

  5. CDC. Update: eradication of paralytic poliomyelitis in the Americas. MMWR 1992;41:681-3.

  6. Salk JE. Requirements for persistent immunity to poliovirus. Transactions of the Association of American Physicians 1956;69:105-

  7. Schonberger LB, Kaplan J, Kim-Farley R, Moore M, Eddins DL, Hatch M. Control of paralytic poliomyelitis in the United States. Rev Infect Dis 1984;6(suppl):424-6.

  8. Schaap GJP, Bijkerk H, Coutinho RA, Kapsenberg JG, van Wezel AL. The spread of wild poliovirus in the well-vaccinated Netherlands in connection with the 1978 epidemic. Prog Med Virol 1984;29:124-40.

  9. CDC. Poliomyelitis prevention. MMWR 1982;31:22-6,31-4.

  10. CDC. Poliomyelitis prevention: enhanced-potency inactivated poliomyelitis vaccine -- supplementary statement. MMWR 1987;48:795-8.

Disclaimer   All MMWR HTML versions of articles are electronic conversions from ASCII text into HTML. This conversion may have resulted in character translation or format errors in the HTML version. Users should not rely on this HTML document, but are referred to the electronic PDF version and/or the original MMWR paper copy for the official text, figures, and tables. An original paper copy of this issue can be obtained from the Superintendent of Documents, U.S. Government Printing Office (GPO), Washington, DC 20402-9371; telephone: (202) 512-1800. Contact GPO for current prices.

**Questions or messages regarding errors in formatting should be addressed to

Page converted: 09/19/98


Safer, Healthier People

Morbidity and Mortality Weekly Report
Centers for Disease Control and Prevention
1600 Clifton Rd, MailStop E-90, Atlanta, GA 30333, U.S.A


Department of Health
and Human Services

This page last reviewed 5/2/01