From July 12, 2000, through September 18, 2001, a total of 21 cases of poliomyelitis (including two fatal cases) were reported from the Caribbean island of Hispaniola, divided between Haiti and the Dominican Republic.1,2 In the Dominican Republic, 13 of 168 reported cases of acute flaccid paralysis (AFP) were confirmed as polio by isolation of poliovirus type 1 from either patients or their healthy contacts. The median age of the patients was 3 years (range: 9 months-14 years). None was vaccinated adequately. The most recent confirmed case-patient in the Dominican Republic had paralysis onset on January 25, 2001. In Haiti, eight of 40 AFP cases were confirmed virologically; seven of the confirmed cases occurred during January-July 2001. The median age of the patients was 7 years (range: 2-12 years). One patient had received at least 3 doses of oral poliovirus vaccine (OPV). The most recent confirmed case occurred in Haiti and the patient had paralysis onset on July 12, 2001. Eighteen AFP cases from the Dominican Republic and three from Haiti are pending final classification.
This outbreak was the first in the Americas since 1991 and was associated with the circulation of a type 1 OPV-derived virus, having substitutions affecting 1.8% to 4.1% of nucleotides encoding the major capsid protein (VP1). The circulating vaccine-derived poliovirus associated with the outbreak recovered the capacity to cause paralytic disease and widespread person-to-person transmission and was biologically indistinguishable from type 1 wild poliovirus. Contemporary vaccine-derived poliovirus isolates from persons with AFP cases in other countries of the Americas are more closely related (>99.5% VP1 sequence similarity) to the respective OPV strains, are unrelated to the Hispaniola outbreak viruses, and show no evidence of extensive person-to-person transmission. The outbreak in Hispaniola occurred in areas of very low OPV coverage.
In response to the outbreak, health authorities in both countries conducted house-to-house vaccination with OPV. Three rounds of mass vaccination campaigns were conducted in the Dominican Republic in December 2000, and February and April 2001. In each round, approximately 1.2 million OPV doses were administered to an estimated population of 1.1 million children aged <5 years. Haiti conducted two rounds of mass vaccination in February and March 2001. However, these campaigns were hampered by logistic difficulties and heavy rains and reached an estimated 40% of the 1.2 million children aged <5 years. During May-July 2001, a door-to-door and school-based campaign among all 2.3 million children aged <10 years was conducted sequentially in all of the country's departments. Preliminary results suggest that 2.4 million OPV doses were administered, and a second door-to-door campaign is under way.
Travelers to the Dominican Republic and Haiti who are not vaccinated adequately are at risk for polio. Travelers should have received poliovirus vaccination according to national vaccination policies.3
Ministry of Health, Pan American Health Organization, Santo Domingo, Dominican Republic. Ministry of Health, Pan American Health Organization, Port-au-Prince, Haiti. Caribbean Epidemiology Center Laboratory, Pan American Health Organization, Trinidad and Tobago. Div of Vaccines and Immunization, Pan American Health Organization, Washington, DC. Respiratory and Enteric Viruses Br, Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases; Vaccine Preventable Disease Eradication Div, National Immunization Program, CDC.
Update: Outbreak of Poliomyelitis—Dominican Republic and Haiti, 2000-2001. JAMA. 2001;286(22):2802. doi:10.1001/jama.286.22.2802