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INFLUENZA
VIRUS SURVEILLANCE SUMMARY UPDATE
Week
ending December 21, 2002-Week 51
Carina
Blackmore, M.S. Vet. Med., Ph.D.
Florida: During week 51 (December 15-21, 2002) 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 1.5% which is lower than the
national baseline of 1.9%. Higher flu activity than expected for
this time of year (>2%) was reported by physicians in Alachua, Broward,
Duval, Escambia, Lake, Leon, Monroe, and Polk counties. Influenza A (H1N1) was
reported from Indian River County and Influenza B was reported from Sarasota
County. Positive rapid tests were reported from Miami-Dade County. Earlier this
season, influenza A (H1N1) viruses were detected in Broward, Holmes Indian River
and Leon counties, influenza A (H3N2) in Indian River County and influenza B
from Leon and St Johns counties. Positive rapid tests have been reported from
Bay, Broward and Duval counties.
National report: Ten isolates (4 influenza A and 6
influenza B viruses) were made from 1301 specimens tested by the World Health
Organization (WHO) and National Respiratory and Enteric Virus Surveillance
System (NREVSS) collaborating laboratories this week. Since September 29, 0.7%
(n=142) of the 19,817 specimens tested nationwide have been positive. Fifteen
(35%) of the 33 influenza A viruses have been subtyped; 13 were influenza A H1
viruses and 2 was an influenza A (H3N2). Influenza A activity has been detected
in California, Florida, Hawaii, Louisiana, Massachusetts, Nebraska, New York,
North Carolina, Oregon, South Carolina, Texas, Virginia, Washington and
Wisconsin. Influenza B isolates have been identified in Arkansas, Arizona,
California, Indiana, Louisiana, New York, North Carolina, Oklahoma, South
Carolina and Texas. CDC has characterized four influenza A (H1N1), one influenza
A (H1N2), two influenza A (H3N2) and 17 influenza B isolates antigenically. All
strains were similar antigenically to corresponding vaccine strains. The
proportion of patient visits to sentinel physicians for influenza-like illness (ILI)
was 1.3% nationwide. The State and Territorial Epidemiologists reported
widespread flu activity in Texas. Outbreaks were reported from Arkansas, Kansas,
Massachusetts and Virginia. Sporadic influenza activity was reported from 22
states. 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
51. This percentage is
below the epidemic threshold of 7.7% for this time.
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