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INFLUENZA
VIRUS SURVEILLANCE SUMMARY UPDATE
Week
ending January 25, 2003-Week 4
Carina
Blackmore, M.S. Vet. Med., Ph.D.
Florida: During week 4 (January 19-25, 2003) 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 2.4% which is slightly higher
than the national baseline of 1.9%. An influenza outbreak was
reported from Indian River County this week. Cultures are underway. Higher
flu activity than expected for this time of year (>2%) was also reported
by physicians in Broward, Leon, Monroe, Okaloosa, Orange and Polk counties.
Positive rapid tests were reported from Miami-Dade and Pinellas counties.
During the last 4 weeks influenza A (H1N1) viruses were also detected in
Collier, Indian River, Lake, Leon, Palm Beach, Polk, Seminole and Volusia
counties and influenza B in Hillsborough, Indian River, Okaloosa, Santa
Rosa, Sarasota and St. Johns counties. Since December 15 reports of
influenza A of unknown subtype have come from Alachua, Brevard, Duval, Lee
and Orange counties and positive rapid tests from Alachua, Duval, Indian
River, Miami-Dade, Pasco and Pinellas counties.
National report: One hundred forty eight isolates (83 influenza A and 65 influenza B viruses) were made from 1,475 specimens
tested by the World Health Organization (WHO) and National
Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating
laboratories this week. Since
September 29, 3.5% (n=1,195) of the 33,901 specimens tested nationwide have
been positive. One hundred and thirty-six (36%) of the 375 influenza A
viruses have been subtyped; 116 were influenza A H1 viruses and 20 were
influenza A (H3N2). Influenza A and influenza B viruses have been identified
in 29 states. The majority of influenza B isolates (70%; n=820) were
identified in Texas and Missouri. Ten states (Connecticut, Hawaii, Idaho,
Michigan, New Jersey, Ohio, Oregon, Tennessee, Utah and Wyoming) have
reported only influenza A viruses, and 5 states (Alaska, Arkansas, Kansas,
Kentucky and Nevada) have reported only influenza B viruses. CDC has
characterized 11 influenza A (H1N1), 1 influenza A (H1N2), 18 influenza A
(H3N2) and 47 influenza B isolates antigenically. All strains were similar
to corresponding vaccine strains. The proportion of patient visits to
sentinel physicians for influenza-like illness (ILI) was 2.6% nationwide.
The State and Territorial Epidemiologists in Missouri, Texas and Virginia
reported widespread influenza activity. Flu outbreaks were reported in 14
additional states (Alabama, Arkansas, Colorado, Delaware, Georgia, Kansas,
Mississippi, Nebraska, New York, Oklahoma, South Dakota, Tennessee, Virginia
and Utah). Sporadic influenza activity was reported from 32 states. The
proportion of deaths attributed to pneumonia and influenza as reported by
the vital statistics offices of 122 U.S. cities was 7.3% during week 4. This percentage is
below the epidemic threshold of 8.2% for this time.
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