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—from Epidemiological Bulletin, Vol. 21 No. 4, December 2000— Outbreak of Poliomyelitis in the Dominican Republic and HaitiThe Ministries of Health of the Dominican Republic and Haiti, with the assistance of the Pan American Health Organization (PAHO) and the United States’ Centers for Disease Control and Prevention (CDC), are investigating an outbreak of poliomyelitis on the island of Hispaniola, which is shared by both countries. Between 12 July and 18 November, 2000, 19 persons with acute flaccid paralysis (AFP) were identified in the Dominican Republic, including six laboratory-confirmed cases with poliovirus type 1 isolates. Of the 19 case-patients, 16 (84%) were younger than 6 years of age (range: 9 months—21 years). All case-patients were either unvaccinated (n=14) or inadequately vaccinated (n=5). In Haiti, a single laboratory-confirmed poliovirus type 1 case was reported in an inadequately vaccinated child aged 2 years. The paralysis onset was August 30. Intensive case-finding activities have continued but no additional cases have been identified. This outbreak is of serious concern because no case of polio attributed to wild poliovirus has been detected in the Western Hemisphere since 1991. The outbreak virus is unusual because it is derived from oral poliovirus vaccine (OPV), has 97% genetic similarity to the parental OPV strain (vaccine-derived isolates are normally over 99.5% similar to the parent strain) and appears to have recovered the neurovirulence and transmissibility characteristics of wild poliovirus type 1. In comparison, wild polioviruses normally have less than 82% genetic similarity to OPV. Further, the differences in nucleotide sequences among the outbreak isolates suggest that the virus has been circulating for approximately 2 years in an area where vaccination coverage is very low and the accumulated genetic changes had restored the essential properties of wild poliovirus. In response to the outbreak, the ministries of health of the Dominican Republic and Haiti, with the assistance of PAHO and CDC, are working to determine the extent of the outbreak, evaluate its causes, and put in place appropriate control measures. The Dominican Republic has started a nationwide mass vaccination campaign with OPV. In Haiti, three nationwide vaccination rounds with OPV are planned for January, February, and March 2001. The current outbreak draws attention to the importance that polio-free areas maintain high coverage with polio vaccine until global polio eradication has been achieved. OPV is safe, effective and recommended for the eradication of polio. All countries should maintain high quality AFP and poliovirus surveillance, and current activities to eradicate wild polioviruses should be accelerated. All travelers to the Dominican Republic and Haiti should be fully vaccinated against polio according to national vaccination guidelines. Those that have traveled to these countries and are not adequately immunized should be considered by their health care providers as at risk of acquiring poliomyelitis. Possible cases should be investigated properly, including collection of stool samples, and suspected cases should be reported immediately to state and local health departments. Source: PAHO. Division of Vaccines and Immunization (HVP) Return to the Index, |
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