In 1982, 13,523 Shigella isolations from humans were reported
to
CDC. This represents a 9.9% decrease from the 15,006 isolations
reported in 1981. The number of isolations has continued to
decline
from the 15,334 reported during the peak year, 1978 (Figure 1).
Shigella serotypes were reported for 12,818 of the 13,523
isolates and were distributed by serotype as follows: S.
sonnei--8,228 (64.2%), S. flexneri--4,165 (32.5%), S. boydii--294
(2.3%), and S. dysenteriae--131 (1.0%). S. flexneri 1a, 1b, 2a,
3a,
and 6 comprised 27.3% of all S. flexneri subtyped. When compared
with
1981, reported S. boydii isolations decreased by 42.4%; S.
dysenteriae, by 35.8%; and S. sonnei, by 12.7%. The number of S.
isolates and were distributed by serotype as follows: S.
sonnei--8,228 (64.2%), S. flexneri--4,165 (32.5%), S. boydii--294
(2.3%), and S. dysenteriae--131 (1.0%). S. flexneri 1a, 1b, 2a,
3a,
and 6 comprised 27.3% of all S. flexneri subtyped. When compared
with
1981, reported S. boydii isolations decreased by 42.4%; S.
dysenteriae, by 35.8%; and S. sonnei, by 12.7%. The number of S.
flexneri isolations remained relatively constant.
The decreases were not confined to one state or region. From
1981
to 1982, S. sonnei decreased notably in Florida (166 to 92),
Georgia
(349 to 135), Hawaii (128 to 46), Indiana (102 to 35), Louisiana
(357
to 147), Missouri (128 to 35), and Virginia (889 to 81); S. boydii,
in
Arizona (38 to 16) and Texas (82 to 45); and S. dysenteriae, in
California (129 to 71).
In the reported age distribution of persons from whom isolates
were obtained, the age-specific attack rate was highest for
2-year-old
children, markedly lower for older children, and slightly lower for
adults, except for a slight increase for 20- to 29-year-olds
(Figure
2). In the 20- to 29-year age groups, a slightly higher isolation
rate was reported for females than for males. The isolation rates
by
sex were similar for the remaining age groups. The median ages of
persons from whom isolates were reported were S. boydii--13 years,
S.
dysenteriae--24, S. flexneri--11, and S. sonnei--7.
Since shigellosis is a more important problem for some
population
groups than for 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. Thirty-one percent of the reports included
data
on patient residence at the time of onset of illness. Of those
specified, 1.2% lived in institutions and 2.7% on Indian
reservations. Sixty-nine percent of the reported isolates from
residents of institutions were S. sonnei, and 30.8% were S.
flexneri.
Fifty-nine percent of the isolates from residents of Indian
reservations were S. flexneri, and 40.9% were S. sonnei. S. sonnei
accounted for 74.4% of the isolates with known residence; S.
flexneri,
for 22.9%; S. boydii, for 1.2%; and S. dysenteriae, for 0.5%.
Reported by Statistical Svcs Activity and 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 clincial or sub-clinical infections or between
chronic or convalescent carriers.
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