VIRUS SURVEILLANCE SUMMARY UPDATE
ending April , 2003-Week 13
Blackmore, M.S. Vet. Med., Ph.D.
week 13 (March 23-29, 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 1.48%. 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, Orange, Palm Beach and Polk counties.**
Light to moderate influenza activity was seen in nine other counties
During the last three weeks (weeks 11 13) seven
laboratory confirmed influenza cases. (primarily influenza A (H1N1) and
influenza B) were reported from four counties across the state. This week
influenza A H1N1 viruses were reported Broward county, influenza A of unknown
subtype from Broward county and influenza B from Indian River county.
National report: During week
isolates (75 influenza A and 19 influenza B viruses) were made from 1,465
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 7.6% during Week 13.
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 1.2% nationwide. The State and Territorial Epidemiologists in
19 states (Alaska, Arizona, California, Colorado, Idaho, Maine, Maryland,
Massachusetts, Michigan, Minnesota, Montana, North Dakota, Ohio, Oregon, South
Carolina, South Dakota, Tennessee, Utah, and Wisconsin) reported regional
influenza activity. No flu outbreaks were reported. Twenty-eight states reported
sporadic influenza activity, and 2 states reported no influenza activity.
During the past 3 weeks
(weeks 11-13), between 5.3% and 10.7% of the specimens tested for
influenza in the West South Central, East South Central, Pacific, and South
Atlantic regions were positive, 27.4% of the specimens tested for influenza in
the New England region were positive, between 14.2% and 19.8% of specimens
tested for influenza in the West North Central, Mountain, and East North Central
regions were positive, and less than 5% of specimens tested for influenza in the
Mid-Atlantic region were positive. Since
September 29, 11.8% (n=8,791) of the 74,790 specimens tested nationwide
have been positive. Two thousand one hundred and eighty-nine (49%) of the 4,513
influenza A viruses have been subtyped; 1,661 (76%) were influenza A (H1)
viruses and 528 (24%) were influenza A (H3N2) viruses.
Laboratory confirmed influenza has been reported from all 50 states.
Influenza B viruses were reported more frequently than influenza A
viruses (range 59% - 83%) in the West South Central, South Atlantic, West North
Central, and East South Central regions. 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. However, during the past 3 weeks (weeks 11-13), 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 71 H1 viruses
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.
**The higher than normal Orange county ILI reflects the
report of a single surveillant. We
seek additional surveillants for that area.
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