VIRUS SURVEILLANCE SUMMARY UPDATE
ending April 5 , 2003-Week 14
Blackmore, M.S. Vet. Med., Ph.D.
week 14 (March 30-April 5, 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 1.25%. 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 Indian River and Palm Beach counties. Light
to moderate influenza activity was seen in ten other counties. During the past three weeks (weeks 12
14) three laboratory confirmed influenza cases (primarily influenza B) were
reported from two counties across the state. This week one influenza A H1N1
virus was reported in Palm Beach county and one influenza B from Broward county.
National report: During week
isolates (73 influenza A and 15 influenza B viruses) were made from 1,067
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
7.9% during Week 14. This
percentage is below the epidemic threshold of 8.1% for this time. The proportion
of patient visits to sentinel physicians for influenza-like illness (ILI) was
0.8% nationwide. The State and Territorial Epidemiologists in 10 states
(Colorado, Idaho, Maine, Maryland, Minnesota, Montana, Nevada, North Dakota,
Ohio, and Utah). Thirty-two states and New York City reported sporadic activity,
and 5 states reported no influenza activity.
During the past 3 weeks (weeks 12-14),
between 20.0% and 28.3% of the specimens tested for influenza in the New England
and East North Central regions were positive, between 13.4% and 13.9% of
specimens tested for influenza in the Mountain and West North regions were
positive, and between 2.3% and 7.4% of the specimens tested for influenza in the
West South Central, Mid-Atlantic, East South Central, Pacific, and South
Atlantic regions were positive.
Since September 29, 12.0% (n=9,728) of the
80,968 specimens tested nationwide have been positive.
Two thousand six hundred and twenty-three (50%) of the 5,243 influenza A
viruses have been subtyped; 2,069 (79%) were influenza A (H1) viruses and 563
(21%) 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% - 85%) in the South Atlantic,
West North Central, West South Central, and East South Central regions. However,
during the past 3 weeks (weeks 12-14), influenza A activity has increased to the
point that during those weeks, influenza A viruses were reported more frequently
than influenza B viruses in all nine surveillance regions.
CDC has characterized 76 influenza A (H1N1), 27 influenza A (H1N2), 63
influenza A (H3N2) and 188 influenza B isolates antigenically. The neuraminidase
typing for 123 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).
An 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