INFLUENZA VIRUS SURVEILLANCE SUMMARY UPDATE

Week ending December 1, 2001-Week 48

Carina Blackmore, M.S. Vet. Med., Ph.D.

National report: During week 48 (November 24-December 1, 2001), 3 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 10,747 specimens for influenza viruses have been tested and 99 (0.9%) were positive. Of the 99 isolates identified, 96 were influenza A viruses and 3 were influenza B viruses. Sixty-five (68%) of the influenza A viruses were subtyped, 64 were influenza A (H3N2) and one was an influenza A (H1N1) virus. Fifty-five (56%) of the influenza A isolates were isolated in Alaska. Influenza A has also been identified in Alabama, Arizona, Colorado, Florida, Hawaii, Kentucky, Louisiana, Minnesota, New York, North Carolina, North Dakota, Pennsylvania, South Carolina, Texas, Utah, Washington and Wisconsin. The influenza B isolates were identified in Louisiana, Michigan and Texas.  The proportion of patient visits to sentinel physicians for influenza-like illness (ILI) overall was 1.4%, which is less than 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 6.4% during week 48. This percentage is below the epidemic threshold of 7.5% for this time. Influenza activity was reported as widespread in Alaska and regional in Arizonaa this week. Sporadic activity was reported from 23 states (Alabama, Colorado, Florida, Georgia, Hawaii, Indiana, Iowa, Kansas, Kentucky, Louisiana, Michigan, Minnesota, Missouri, Nevada, New Mexico, New York, North Carolina, Ohio, South Carolina, Tennessee, Utah, Vermont and West Virginia, 18 states reported no influenza activity.

Florida: Influenza activity remains low in Florida and less than one percent 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 48. Influenza-like illness activity was detected in 12 counties from Escambia to Monroe. Higher flu activity than expected for this time of year (>2%) was reported by physicians in Duval, Escambia, Monroe, Palm Beach and Polk counties. Six positive influenza A cultures were reported this week. Influenza A (H3N2) was reported from Broward (2), Duval and StJohn’s Counties. Two influenza A isolates of unknown subtype were reported from Pinellas County. Between September 4 and December 7, influenza A (H2N3) was isolated from 9 patients residing in Broward, Collier, Duval, Palm Beach and St John’s Counties and influenza A of unknown subtype, was isolated from 4 patients in Pinellas County. In addition, positive rapid antigen tests were reported from Duval County (1), Marion (2), Miami-Dade (6) Okaloosa (2) and Volusia (2) Counties.