Current Trends
Human Salmonella Isolates -- United States, 1981
In 1981, 35,625 salmonellae isolations (including Salmonella
typhi) from humans were reported to CDC. This represents an
increase
of 18.7% over the 30,004 isolates reported in 1980. The ten most
frequently isolated serotypes comprised 68.7% of the total isolates
(Table 1). Four of these accounted for 53% of the increase; S.
typhimurium* alone accounted for over 30% (10,443 to 12,176) of the
increase; S. enteritidis for 11% (1,904 to 2,554); S. newport for
8%
(1,651 to 2,134); and S. muenchen for 4% (374 to 644). Increases
were
also reported in some of the less frequently isolated serotypes.
For
example, S. drypool increased 476% (17 to 98 isolations) from 1980;
S.
chester, 231% (55 to 182); S. hadar, 194% (47 to 138); and S.
seftenberg, 138% (87 to 207).
The increase in isolates was not confined to one state or
region.
California, Georgia, Illinois, Louisiana, Massachusetts, Michigan,
New
York, and Ohio, accounted for 71% of the 18.7% increase. For some
serotypes, increases were attributed to outbreaks in one or more
states. Michigan and Ohio accounted for 44.8% of the increase in
S.
muenchen, part of which may be attributed to an outbreak associated
with marijuana contaminated with S. muenchen (1). Seventy-nine
percent of the increase in S. chester occurred in Massachusetts and
Vermont; an outbreak associated with this serotype was traced to
roast
beef in Vermont (2). A 39% increase in S. newport occurred in New
Jersey, Pennsylvania, and Washington; increases were associated
with
eating pre-cooked roast beef in New Jersey and Pennsylvania (3).
An
outbreak of S. newport was reported in Washington, but no vehicle
was
identified. Eighty-seven percent of the increase in S. drypool
occurred in California, Ohio, and Texas; outbreaks were reported in
Ohio and Texas (4). Illinois, which accounted for 90% of the
increase
in S. seftenberg, reported an outbreak of this serotype in a prison
system. Increases in S. hadar, S. typhimurium, and S. enteritidis
were not confined to any single state.
*Includes S. typhimurium var. copenhagen
Figure 1 shows the reported age distribution of persons from
whom
isolates were obtained. The rate was highest for 2- to 4-month old
infants, decreased abruptly among age groups of early childhood,
and
then remained constant through the adult years. The rate of
Salmonella isolation was slightly higher among males than among
females in the 20-year age groups; it was slightly higher among
females than among males in the 20-69 year age groups. This is
consistent with data from previous years. The increase in reported
isolates occurred in all age groups; however, the largest increases
occurred in the 20-29, 30-39, and 40-49-year age groups. During
the
past 14 years, the median age of all persons from whom isolates
were
obtained has continued to increase, from a median of 6 years in
1968
to 12 years in 1981. Table 1 reports the median age of persons
from
whom isolates were obtained for the 10 serotypes of Salmonella most
frequently isolated.
In 1981, 38 of 604 reported isolates of S. typhi were from
carriers, 195 from cases, and the remaining 371, undesignated. The
carriers' median age was 61.0, while that of the new cases was
23.0.
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 the Salmonella
Surveillance
Activity conducted by the Association of State and Territorial
Epidemiologists and by CDC. It is a passive laboratory-based
system
that receives weekly reports from the 50 states and the District of
Columbia and regular summaries from the U.S. Department of
Agriculture. The reports do not distinguish between clinical and
subclinical infections or between chronic and convalescent
carriers.
Many selective factors affect whether an infection will be
reported.
Despite such restrictions, these data provide a basis for
comparison
with past and future tabulations.
The number of reported Salmonella isolations has been steadily
increasing since 1977, but the 1981 annual increase of 18.7% is
larger
than in previous years. Some of this may be artifactual, but
increases seen annually are probably not all the result of
artifacts.
The disproportionately greater increase among young adults in
certain
states suggests possible recent increases in exposure of this age
group to specific contaminated vehicles in certain areas of the
country. The gradual increase in the median age of all cases of
salmonellosis in the last few years may also indicate a shift in
relative rates of exposure of different age groups to contaminated
vehicles.
In many outbreaks, the cause was a relatively uncommon
serotype,
which points to the importance of serotyping Salmonella. Recent
application of molecular biologic techniques to epidemiologic
studies
has assisted in providing means of identifying outbreaks caused by
common serotypes, and further uses of these techniques are
currently
being evaluated. In this way, the surveillance data will serve as
indicators of the effectiveness of various public health control
measures.
References
Taylor DN, Wachsmuth IK, Shangkuan Y-H, et al. Salmonellosis
associated with marijuana: a multistate outbreak traced by
plasmid
fingerprinting. N Engl J Med 1982;306:1249-53.
CDC. Multiple outbreaks of salmonellosis associated with
precooked
roast beef--Pennsylvania, New York, Vermont. MMWR
1981;30:569-70.
CDC. Multistate outbreak of salmonellosis caused by precooked
roast beef. MMWR 1981;30:391-2.
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