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INFLUENZA
VIRUS SURVEILLANCE SUMMARY UPDATE
Week
ending December 14, 2002-Week 50
Carina
Blackmore, M.S. Vet. Med., Ph.D.
Florida: During week 50 (December 8-14, 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 1.0% which is lower than the
national baseline of 1.9%. Higher flu activity than expected for
this time of year (>2%) was reported by physicians in Duval, Orange, Palm
Beach and Seminole counties. Two influenza isolates (influenza B from St Johns
County and influenza A (H1N1) from Indian River County). Earlier this season,
influenza A (H1N1) viruses were detected in Broward, Holmes Indian River and
Leon counties, influenza A (H3N2) in Indian River County and influenza B from
Leon and St Johns counties. Positive rapid tests have been reported from Bay,
Broward, Duval and Miami-Dade counties.
National report: Thirty isolates (3 influenza A and 27
influenza B viruses) were made from 929 specimens tested by the World Health
Organization (WHO) and National Respiratory and Enteric Virus Surveillance
System (NREVSS) collaborating laboratories this week. Since September 29, 0.7%
(n=113) of the 15,429 specimens tested nationwide have been positive. Fifteen
(35%) of the 33 influenza A viruses have been subtyped; 13 were influenza A H1
viruses and 2 was an influenza A (H3N2). Influenza A activity has been detected
in California, Florida, Hawaii, Louisiana, Massachussetts, Nebraska, New York,
North Carolina, Oregon, South Carolina, Texas, Virginia, Washington and
Wisconsin. Influenza B isolates have been identified in Arkansas, Arizona,
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 Arkansas, Kansas and Colorado.
Sporadic influenza activity was reported from 23 states and 23 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 6.6% during week
50. This percentage is below the epidemic threshold of 7.7%
for this time.
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