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Outbreak of Poliomyelitis -- Angola, 1999

On March 23, 1999, the Pediatric Hospital in Luanda, Angola, reported 21 cases (three deaths) of acute flaccid paralysis (AFP). By April 3, 102 AFP cases had been reported in Luanda and neighboring areas of Bengo province. A preliminary investigation by the Ministry of Health (MOH) indicated that these cases primarily occurred among children aged less than 5 years; 90% had received two or fewer doses of oral poliovirus vaccine (OPV), 4% had received three doses, and 6% had received four doses. Many case-patients resided in overcrowded municipalities where families displaced by civil war had settled. On the basis of preliminary data, MOH suspected the outbreak was poliomyelitis and began planning a vaccination campaign to control the epidemic. Surveillance was strengthened to identify and rapidly investigate reports of AFP cases to determine the extent of the outbreak.

On April 8, the National Institute of Virology in South Africa isolated wild poliovirus type 3 from 11 (50%) of 22 stool specimens from AFP cases submitted by MOH. By April 11, the number of AFP cases increased to 276 (19 deaths). By April 25, 634 AFP cases (39 deaths) were reported. Field investigations confirmed two cases of AFP in children aged less than 5 years in Benguela, a city approximately 300 miles (480 km) south of Luanda. On April 17 and 18, a mass vaccination campaign was carried out targeting 526,036 children. OPV was administered to 634,368 children aged less than 5 years in Luanda and the rest of the province. A World Health Organization (WHO) team is assisting with the investigation of the outbreak. Three rounds of National Immunization Days (NIDs) * at monthly intervals are planned to begin in July.

Reported by: Ministry of Health, Luanda, Angola. World Health Organization, Luanda, Angola. Regional Office for Africa, World Health Organization, Harare, Zimbabwe. Vaccines and Other Biologicals Dept, World Health Organization, Geneva, Switzerland. National Institute of Virology, Univ of the Witwatersrand, Johannesburg, South Africa. Respiratory and Enterovirus Br, Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases; Vaccine Preventable Disease Eradication Div, National Immunization Program, CDC.

Editorial Note

Editorial Note: The outbreak in Angola represents one of the largest epidemics of poliovirus type 3 in the vaccine era and one of the largest polio epidemics recorded in Africa (1). Preliminary data from the investigation suggest that the outbreak primarily resulted from failure to vaccinate, with a high proportion (approximately 90%) of case-patients being unvaccinated or partially vaccinated (three or fewer doses of OPV).

With the intensification of civil war at the end of 1998, large groups of displaced persons moved from areas where vaccination services had been suboptimal to the capital, Luanda, and other cities. Sub-National Immunization Days (SNIDs) ** were conducted in national and provincial capitals of Angola in 1996, and NIDs were conducted in districts under government control: 147 (89%) of 165 districts in 1997, and 121 (73%) of 165 districts in 1998 (2,3). Excluding districts not under government control from the denominator, greater than or equal to 90% coverage was obtained in each round of NIDs. Estimated vaccination coverage for the 1998 NIDs was less than 50% in three of Angola's 18 provinces.

Displaced persons settled in crowded areas where sanitation is poor and water supply inadequate and created an ideal environment for the spread of poliovirus. Movement of refugees out of the country increases the probability that the epidemic will spread into neighboring countries, some of which have been reporting no cases of polio. These countries have been informed and are increasing surveillance in border zones and developing plans to vaccinate refugee children from Angola.

Travelers to Angola are advised to review their polio vaccination history to ensure that they have received a complete primary series of three doses before initiating travel (4). In addition, travelers who already have received a complete primary series should receive an additional dose of either inactivated poliovirus vaccine (IPV) or OPV before leaving for Angola. If there is insufficient time before travel to administer a three-dose primary vaccination series, then travelers should receive a minimum of a dose of either IPV or OPV, depending on age and vaccination history (4).

To achieve the target of polio eradication by 2000, implementation of polio eradication strategies in Angola needs to be accelerated and to reach all areas of the country, including those not under government control. The planned three rounds of NIDs during July-September are a significant step in this direction, but success will depend on achieving high vaccination coverage levels in all areas of the country. In Angola and other countries in conflict, reaching agreements for cease fires to carry out vaccination campaigns for polio eradication are becoming increasingly urgent.

References

  1. Patriarca PA, Sutter RW, Oostvogel PM. Outbreaks of paralytic poliomyelitis, 1976-1995. J Infect Dis 1997;175(suppl 1):S165-S172.

  2. Izurieta HS, Biellik RJ, Kew OM, Valente FL, Schoub BD, Sutter RW. Poliomyelitis in Angola: current status and implications for the eradication of poliovirus in southern Africa. J Infect Dis 1997;175(suppl 1):S24-S29.

  3. CDC. Progress toward poliomyelitis eradication -- African region, 1997. MMWR 1998;47:235-9.

  4. CDC. Poliomyelitis prevention in the United States: introduction of a sequential vaccination schedule of inactivated poliovirus vaccine followed by oral poliovirus vaccine: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 1997;46(no. RR-3): 1-25.

Nationwide mass campaigns over a short period (days to weeks), in which two doses of oral poliovirus vaccine are administered to all children in the target age group (usually aged less than 5 years), regardless of vaccination history, with an interval of 4-6 weeks between doses. ** Focal mass campaigns in high-risk areas over a short period (days to weeks) in which two doses of OPV are administered to all children in the target age group, regardless of vaccination history, with an interval of 4-6 weeks between doses.


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