Yellow Fever Update

Article excerpt

In 1991, a total of 2696 cases of yellow fever were reported to WHO. As in recent years, the vast majority were from Africa (2561 cases), while South American countries reported 135 cases. A total of 737 deaths due to yellow fever were reported in 1991: 661 in Africa (case-fatality rate (CFR), 26%) and 76 in South America (CFR, 56%). The overall CFR was 27%. A summary of the number of yellow fever cases and deaths reported to WHO by Member States for the period 1988-91 is shown in Table 1.

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Africa

Only Nigeria reported yellow fever activity in 1991, as in 1989. Six suspect cases originally reported from Niger from 1990 have now been withdrawn from the official recording of reported cases because of lack of evidence that these cases were really due to yellow fever virus.(d) Since 1965 more than 10 yellow fever outbreaks in Africa have affected primarily children.

Nigeria. A total of 2561 cases of yellow fever were reported from 12 states during 1991. Four states (Kano, Katsina, Bendel and Borno) accounted for 97% of the reported cases. Cases were recorded during all months of the year, except January; however, the vast majority occurred during October, when over 1000 cases were reported. One-quarter of the reported cases occurred among under-5-year-olds and an additional 29% involved 5-14-year-olds. The distribution of cases by sex was approximately equal, with 1112 males (52%) and 1038 females (48%). The sex of the remaining 411 cases was not reported.

Incorporation of yellow fever vaccine into EPI: progress as of March 1993. In 1989 the Global Advisory Group of WHO/EPI recommended that the 33 African countries at risk for yellow fever include yellow fever vaccine in their routine childhood immunization programmes. Based on data reported to WHO as of March 1993, 17 of these countries at risk now have a policy to incorporate yellow fever vaccine into their EPI.

As of March 1993, 12 of these countries reported yellow fever vaccine coverage. In 1992, a total of almost 2 million (11%) of the 18.7 million surviving infants in African countries at risk for yellow fever received a dose of vaccine. This compares with a measles vaccine coverage of 53% for children under 1 year of age in the same 33 countries. Since most countries administer yellow fever vaccine at the same visit as measles vaccine, this level of coverage for yellow fever vaccine should be easily attained. Countries that incorporate yellow fever vaccine into their EPI should monitor coverage and include yellow fever vaccine in immunization coverage surveys.

* Materials on integration of yellow fever vaccine into EPI are available from the Expanded Programme on Immunization, World Health Organization, 1211 Geneva 27, Switzerland.

South America

In 1991, a total of 135 cases and 76 deaths (CFR, 56%) were officially reported from South America. This is similar to that reported in recent years, when the annual number of cases ranged from a low of 90 in 1990, to a high of 235 in both 1987 and 1988. In general, CFRs have been higher in South America in recent years than those typically seen in Africa; between 1988 and 1990, CFRs in South America ranged from 77% to 84%, while those in Africa ranged from 8% to 31%. The ratio of male-to-female cases ranged from 1:1 for Brazil to 10:1 for Bolivia. Overall, the sex ratio was six male cases for each female case reported. The age distribution of cases did not show obvious clustering, with cases reported in all age groups, ranging from a low of nine in the 0-9-year age group, to a high of 41 among those aged 20-29 years. …