VIRUS SURVEILLANCE SUMMARY UPDATE
ending February 1, 2003 - Week 5
Blackmore, M.S. Vet. Med., Ph.D.
ending February 1, 2003-Week 5
During week 5 (January 25-February 1, 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 2.5% which is slightly higher than the
national baseline of 1.9%. Higher flu activity than expected for this time
of year (>2%) was also reported by physicians in Duval, Indian River,
Lake, Leon, Monroe, Okaloosa, Orange, Polk and Sarasota counties.
Influenza A (H1N1) viruses were reported from Duval, Lake and St Johns
counties, influenza H3N2 from Leon County and influenza B viruses were
reported from Duval, Indian River, Orange and St Johns counties this
week. Positive rapid tests were reported from Orange and Pinellas
counties. During the last 4 weeks influenza A (H1N1) has also been
reported from Broward, Leon, Okaloosa, Orange, Palm Beach and Volusia
counties, influenza A of unknown subtype from Alachua and Pinellas
counties and influenza B from Hillsborough, Okaloosa, Pinellas, Santa Rosa
and Sarasota counties.
National report: One hundred
sixty-six isolates (49 influenza A and 117 influenza B viruses)
were made from 1,157 specimens tested by the World Health Organization
(WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS)
collaborating laboratories this week. Since September 29, 4.7%
(n=1,714) of the 36,753 specimens tested nationwide have been positive.
Two hundred and thirty-seven (44%) of the 543 influenza A viruses have
been subtyped; 192 were influenza A H1 viruses and 45 were influenza A
(H3N2). Laboratory confirmed influenza has been reported from 47 states.
The majority of influenza B isolates (70%; n=820) were identified in Texas
and Missouri. Influenza A viruses were reported more frequently than
influenza B viruses (range 63%-85%) in the Mountain, New England, East
North Central, Pacific, and Mid-Atlantic regions. CDC has characterized 34
influenza A (H1N1), 15 influenza A (H1N2), 23 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 2.5% nationwide.
The State and Territorial Epidemiologists in six states (Alabama,
Colorado, Missouri, Tennessee, Texas and Virginia) reported widespread
influenza activity. Flu outbreaks were reported in 18 additional states
(Arkansas, Delaware, Florida, Georgia, Iowa, Kansas, Louisiana, Minnesota,
Mississippi, Nebraska, New Mexico, New York, Oklahoma, Pennsylvania, Rhode
Island, South Dakota, Washington and Utah). Sporadic influenza activity
was reported from 24 states. The proportion of deaths attributed to
pneumonia and influenza as reported by the vital statistics offices of 122
U.S. cities was 7.2% during week 5. This percentage is below the epidemic
threshold of 8.2% for this time.