VIRUS SURVEILLANCE SUMMARY UPDATE
ending April 12 , 2003 - Week 15
Blackmore, M.S. Vet. Med., Ph.D.
week 15 (April 6-12, 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 1.40%. This 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 Duval, Indian River, Palm Beach and Polk counties.
Light to moderate influenza activity was seen in seven other counties.
During the past three weeks (weeks 13 - 15) four laboratory
confirmed influenza cases (primarily influenza B) were reported from three
counties across the state. No new cases of influenza were confirmed by
laboratory reports this week.
National report: During
week 15, nineteen
isolates (18 influenza A and 1 influenza B viruses) were made from 722
specimens tested by the World Health Organization (WHO) and National Respiratory
and Enteric Virus Surveillance System (NREVSS) collaborating laboratories this
week. The proportion of deaths attributed to pneumonia and
influenza as reported by the vital statistics offices of 122 U.S. cities was
7.3% during Week 15. This
percentage is below the epidemic threshold of 8.0% for this time. The proportion
of patient visits to sentinel physicians for influenza-like illness (ILI) was
0.9% nationwide. The State and Territorial Epidemiologists
in Alaska reported widespread activity, 9 states (Colorado, Idaho,
Maryland, Massachusetts, Minnesota, Montana, New York, North Dakota, and Ohio)
reported regional activity. Twenty-seven states reported sporadic activity, and
9 states reported no influenza activity.
During the past 3 weeks (weeks 13-15),
25.0% of the specimens tested for influenza in the New England region and 18.8%
of specimens tested in the East North Central region were positive.
Between 5.0% and 10.8% of the specimens tested for influenza during the
past 3 weeks in the South Atlantic, Pacific, and West North Central regions were
positive, and less than 5.0% of the specimens tested for influenza during the
past 3 weeks in the Mid-Atlantic, East South Central, West South Central, and
Mountain regions were positive.
September 29, 11.8% (n=9,926) of the 83,819 specimens tested nationwide
have been positive. Two thousand
seven hundred and forty-seven (50%) of the 5,480 influenza A viruses have been
subtyped; 2,156 (78%) were influenza A (H1) viruses and 591 (22%) were influenza
A (H3N2) viruses. Laboratory
confirmed influenza has been reported from all 50 states.
Influenza A viruses were reported more frequently than influenza B
viruses (range 56% - 88%) in the New England, East North Central, Mountain,
Pacific, and Mid-Atlantic regions, and influenza B viruses were reported more
frequently than influenza A viruses (range 59% - 81%) in the West South Central,
South Atlantic, West North Central, and East South Central regions.
However, during the past 3 weeks (weeks 13-15), influenza A viruses were
reported more frequently than influenza B viruses in all surveillance regions
except the New England region.
CDC has characterized 140 influenza A (H1N1), 46 influenza
A (H1N2), 82 influenza A (H3N2) and 188 influenza B isolates antigenically. The
neuraminidase typing for 42 H1 viruses is pending. All influenza A strains were similar to corresponding
vaccine strains. One influenza B strain was more similar to B/Shizuoka/15/01
than to the vaccine strain (B/Hong Kong/ 330/01).
avian flu virus strain, influenza A H5N1, has been recovered from two influenza
cases in Hong Kong. CDC has issued recommendations on increased influenza
surveillance in the United States. Of
particular importance is to consider influenza cultures on patients, with recent
travel histories to Asia, who are hospitalized with unexplained pneumonia, acute
respiratory distress syndrome or severe respiratory illness.
* Reporting is incomplete for this week. Numbers may change
as more reports are received.
For additional information on influenza and influenza
surveillance results, please visit our website at http://www.doh.state.fl.us/disease_ctrl/epi/htopics/flu/index.htm