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Current Trends Shigellosis -- United States, 1984

In 1984, 12,790 Shigella isolates from humans were reported to CDC. This is a 14.4% decrease from the 14,946 isolates reported in 1983. The number of isolates continues to be less than the 15,334 reported during the peak year, 1978 (Figure 2).

Shigella serotypes were reported for 12,179 of the 12,790 isolates. The most frequently isolated serotype, S. sonnei, comprised 64.4% of all isolates serotyped (Table 3). S. flexneri 1a accounted for 14.1% of all S. flexneri subtyped; 1b, 2.6%; 2a, 28.1%; 3a, 24.3%; and 6, 13.3%.

The number of reported isolates in every serotype decreased, compared with the numbers reported in 1983 (Table 3). S. sonnei decreased 15.3%; S. flexneri, 10.8%; S. boydii, 6.5%; and S. dysenteriae, 3.2%. The decreases were not confined to one state or region.

The age-specific rate of reported isolates per 100,000 population was highest for 2-year- old children, lower for older children, and lowest for adults. The age-specific rate for 20- to 29-year-olds was slightly higher than the rates for the older children and the remaining age groups (Figure 3). In addition, in the 20- to 29-year-age group, a slightly higher rate was reported for females than for males. Rates of reported isolates by patient sex were similar for the remaining age groups.

Since some populations have higher rates than others, data were tabulated separately for patients residing in certain institutions (e.g. nursing homes, facilities for the mentally ill, and other resident-care centers) and on American Indian reservations. Only 2,416 (18.9%) of the reports included data on residence at the time of onset of illness. Of those specified, 22 (0.9%) lived in institutions, and 67 (2.8%), on Indian reservations. Fifteen (68.2%) of the reported isolates from residents of institutions were S. sonnei, and five (22.7%) were S. flexneri. Twenty-four (36.4%) of the reported isolates from Indian reservation residents were S. sonnei, and 42 (63.6%) were S. flexneri. For other known residences, S. sonnei accounted for 1,634 (71.7%); S. flexneri, for 587 (25.8%); S. boydii, for 34 (1.5%); and S. dysenteriae, for 24 (1.1%). Reported by Statistical Svcs Activity, Enteric Diseases Br, Div of Bacterial Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: This report is based on CDC's Shigella Surveillance Activity, a passive laboratory-based system that receives reports from the 50 states and the District of Columbia. These reports do not distinguish between clinical or subclinical infections or between chronic or convalescent carriers.

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