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INFLUENZA
VIRUS SURVEILLANCE SUMMARY UPDATE
Week
ending December 29, 2001-Week 52
Carina
Blackmore, M.S. Vet. Med., Ph.D.
National report: During week 52 (December 23-29, 2001),
20 of 608 specimens tested by the World Health Organization (WHO) and National
Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating
laboratories across the United States were positive for influenza. Since
September 30, a total of 17,212 specimens for influenza viruses have been tested
and 356 (2.2%) specimens from 36 states were positive. Of the 356 isolates
identified, 343 (96%) were influenza A viruses and 13 (4%) were influenza B
viruses. Two hundred and nine (61%) of the influenza A viruses were subtyped,
203 were influenza A (H3N2) and 6 were influenza A (H1N1) viruses. One
hundred and ninety-eight (56%) of the 356 influenza viruses isolated were from
the Pacific region. (Alaska, California, Hawaii, Oregon, and Washington) and 136
(38%) of the 356 viruses isolated were identified in Alaska. The
proportion of patient visits to sentinel physicians for influenza-like illness
(ILI) overall was 2.5%, which is above the national baseline of 1.9%. The
proportion of deaths attributed to pneumonia and influenza as reported by the
vital statistics offices of 122 U.S. cities was 7.0% during week 52. This
percentage is below the epidemic threshold of 7.9% for this time. Influenza
activity was reported as widespread in Colorado and regional in Connecticut,
Pennsylvania and Utah this week. Sporadic activity was reported from 42 states
and New York.
Florida: Influenza activity appears to be increasing in
Florida with 2.3% of patients seeking care by physicians in the influenza
sentinel surveillance met the case definition for ILI (> 100 F + cough and or
sore throat) during week 52 compared to 1.3% during week 51. Influenza-like
illness activity was detected in 13 counties from Leon to Monroe. Higher flu
activity than expected for this time of year (>2%) was reported by physicians
in Broward, Duval, Hillsborough, Lake, Leon, Monroe, Palm Beach, Polk and
Sarasota counties. Five cases of influenza A (H2N3) were confirmed from Duval,
Pinellas and Indian River Counties this week. An untyped influenza A from Palm
Beach and six positive rapid antigen tests from Hillsborough County were also
reported this week. Between September 4 and December 27, influenza A
(H3N2) was isolated from 16 patients residing in Broward, Collier, Duval,
Hillsborough, Indian River, Palm Beach, Pinellas, Polk, and St Johns Counties
and infections with influenza A of unknown subtype, was diagnosed in patients in
Gadsden, Martin, Pinellas, Palm Beach and Hillsborough County. Influenza B was
isolated from 2 patients in Hillsborough County. In addition, positive rapid
antigen tests were reported from Duval County (1), Hillsborough (11), Palm Beach
(1), Marion (8), Miami-Dade (13) Okaloosa (2) and Volusia (6) Counties.
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