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INFLUENZA
VIRUS SURVEILLANCE SUMMARY UPDATE
Week
ending January 18, 2003-Week 3
Carina
Blackmore, M.S. Vet. Med., Ph.D.
Florida: During week 3 (January 12-18, 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 2.0% which is slightly higher
than the national baseline of 1.9%. Higher flu activity than
expected for this time of year (>2%) was reported by physicians in Broward,
Indian River, Leon, Monroe, Okaloosa, Orange and Polk counties. Influenza A
(H1N1) was reported from Palm Beach County and influenza A of unknown subtype
was reported from Alachua, Duval and Lee counties this week.
Influenza B was reported from Indian River and Santa Rosa counties.
During the last 4 weeks influenza A (H1N1) viruses were also detected in
Collier, Indian River, Lake, Leon, Polk, Seminole and Volusia counties and
influenza B in Hillsborough, Okaloosa, Sarasota and St. Johns counties. Since
December 15 reports of influenza A of unknown subtype have come from Brevard and
Orange counties and positive rapid tests from Alachua, Duval, Indian River,
Miami-Dade and Pinellas counties.
National report: One hundred fifty isolates (36 influenza A and 114 influenza B viruses) were made from 1,414 specimens
tested by the World Health Organization (WHO) and National
Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating
laboratories this week. Since
September 29, 2.2% (n=950) of the 30,942 specimens tested nationwide have been
positive. Ninety-three (39%) of the 241 influenza A viruses have been subtyped;
78 were influenza A H1 viruses and 15 were influenza A (H3N2). Influenza A and
influenza B viruses have been identified in 21 states (Arizona, California,
Colorado, Delaware, Florida, Iowa, Indiana, Louisiana, Massachusetts, Missouri,
Montana, Nebraska, New Mexico, New York, North Carolina, Oklahoma, South
Carolina, Texas, Virginia, Washington and Wisconsin). Foureen states (Alabama,
Connecticut, Hawaii, Illinois, Michigan, Minnesota, New Jersey, Ohio, Oregon,
South Dakota, Tennessee, Utah, Vermont and Wyoming have reported only influenza
A viruses, and 7 states (Arkansas, Kansas, Kentucky, New Hampshire, Nevada,
Pennsylvania and West Virginia) have reported only influenza B viruses. CDC has
characterized 11 influenza A (H1N1), 1 influenza A (H1N2), 18 influenza A (H3N2)
and 32 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 1.5% nationwide. The State and
Territorial Epidemiologists in Missouri, North Carolina and Texas reported
widespread influenza activity. Flu outbreaks were reported in 11 additional
states (Alabama, Arkansas, Colorado, Georgia, Kansas, Nebraska, New York,
Oklahoma, South Dakota, Tennessee and Virginia). Sporadic influenza activity was
reported from 33 states. The proportion of deaths attributed to pneumonia and
influenza as reported by the vital statistics offices of 122 U.S. cities was
7.5% during week 3. This percentage is below the epidemic threshold of 8.1%
for this time.
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