In 1981, 15,006 Shigella isolations from humans were reported
to
CDC. While this represented a 6% increase over the 14,168 isolates
reported in 1980, it remained 2% below the 15,334 reported during
the
peak year, 1978 (Figure 4).
Shigella serotypes were reported for 14,278 of the 15,006
isolates
and were distributed by serotype as follows: S. sonnei --9,423
(66%),
S. flexneri --4,141 (29%), S. boydii --510 (3.6%), and S.
dysenteriae
--204 (1.4%). When compared with 1980, this represented increases
of
46% for S. boydii, 39% for S. dysenteriae, and 9% for S. sonnei,
and a
decrease of 5% for S. flexneri. The increases were not confined to
one state or region. From 1980 to 1981 S. sonnei increased notably
in
Connecticut (67 to 337), Missouri (50 to 128), Virginia (83 to
889),
and Washington (161 to 307); S. boydii increased in Texas (43 to
82).
The reported age distribution* of persons from whom isolates
were
obtained is shown in Figure 5. The rate, highest for 2-year-old
children, decreased abruptly for older children and decreased more
gradually for adults, except for a slight increase for 20-29
year-olds. Although in the 20-29-year age group a slightly higher
isolation rate was reported for women, the isolation rates by sex
were
similar. The median ages in years of persons from whom isolates
were
reported were S. boydii--9.0, S. dysenteriae--16.5, S.
flexneri--10.0,
and S. sonnei--6.0.
*Age, sex, and type of residence were unavailable for California.
Since shigellosis is a more significant 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. Twenty-nine percent of the
reports
included data on patient residence at the time of illness onset:
0.9%
lived in institutions and 1.5% on Indian reservations.
Seventy-four
percent of the reported isolates from residents of institutions
were
S. flexneri, and 26% were S. sonnei. Similarly, 69% of the
isolates
from residents of Indian reservations were S. flexneri, and 31%
were
S. sonnei. This contrasts with the remainder of Shigella cases
with
known residence in which S. sonnei represented 75% of isolates and
S.
flexneri represented 22.5%.
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 sub-clinical infections or between
chronic or convalescent carriers.
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