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INFLUENZA
VIRUS SURVEILLANCE SUMMARY UPDATE
Week
ending December 7, 2002-Week 49
Carina
Blackmore, M.S. Vet. Med., Ph.D.
Florida: During week 49 (December 1-7, 2002) influenza
activity, calculated based on the proportion of patients with influenza-like
illness (ILI) seeking care by physicians participating in the Florida Sentinel
Physicians Surveillance Network was 1.5%. Although the activity is increasing
over time it is below the national baseline of 1.9%. Higher flu activity
than expected for this time of year (>2%) was reported by physicians in
Broward, Duval, Leon, Okaloosa, Orange, Palm Beach, Polk and Seminole counties.
Two influenza isolates (influenza B from St Johns County and influenza A (H1N1)
from Indian River County) were reported this week. Influenza cases confirmed by
rapid tests were also reported from Leon (A, B) and Miami-Dade counties. Earlier
this season, influenza A (H1N1) viruses were detected in Broward, Holmes and
Leon counties and influenza A (H3N2) in Indian River County.
National report: Twenty-four isolates (5 influenza A and 19 influenza B viruses) were made from 819 specimens
tested by the World Health Organization (WHO) and National
Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating
laboratories this week. Since
September 29, 0.6% (n=82) of the 13,958 specimens tested nationwide have been
positive. Twelve (40%) of the 30 influenza A viruses have been subtyped; 10 were
influenza A H1 viruses and 2 was an influenza A (H3N2). Influenza A activity has
been detected in California, Florida, Hawaii, Louisiana, Nebraska, New York,
North Carolina, Oregon, South Carolina, Texas, Virginia, Washington and
Wisconsin. Influenza B isolates have been identified in Arkansas, California,
Louisiana, New York, North Carolina, Oklahoma, South Carolina and Texas. CDC has
characterized four influenza A (H1N1), one influenza A (H1N2), two influenza A
(H3N2) and 17 influenza B isolates antigenically. All strains were similar
antigenically to corresponding vaccine strains. The proportion of patient visits
to sentinel physicians for influenza-like illness (ILI) was 1.3% nationwide. The
State and Territorial Epidemiologists reported widespread flu activity in Texas.
Outbreaks were reported from Tennessee. Sporadic influenza activity was reported
from 23 states and 25 states reported no activity. The proportion of deaths
attributed to pneumonia and influenza as reported by the vital statistics
offices of 122 U.S. cities was 7.1% during week 49. This percentage is
below the epidemic threshold of 7.6% for this time.
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