VIRUS SURVEILLANCE SUMMARY UPDATE
ending May 17, 2003-Week 20
Covey, Department of Health, Bureau of Laboratories reports that the following
week 20 (May 11-17, 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 0.73%. This is lower than the national baseline of 1.9%. Higher flu
activity than expected for this time of year (>2%) was reported by
surveillants in Indian River and Polk counties. Light to moderate influenza activity was seen in five other
National report: During
week 20, four isolates (3 influenza A and 1 influenza B viruses) were made
from 511 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 6.3% during Week 20.
This percentage is below the epidemic threshold of 7.5% 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 Massachusetts reported regional influenza activity. Twenty-one states,
New York City and Washington D.C. reported sporadic activity, and 24 states
reported no influenza activity.
Since September 29, 11.6% (n=11,027) of the 94,966 specimens
tested nationwide have been positive. Three
thousand three hundred and eighty-one (53%) of the 6,324 influenza A viruses
have been subtyped; 2,534 (75%) were influenza A (H1N1 and H1N2) viruses and 847
(25%) were influenza A (H3N2) viruses. Influenza
A viruses were reported more frequently than influenza B viruses (range 58% -
86%) in the New England, East North Central, Pacific, Mountain, and Mid-Atlantic
regions, and influenza B viruses were reported more frequently than influenza A
viruses (range 53% - 78%) in the West North Central, West South Central, South
Atlantic, and East South Central regions.
CDC has characterized 173 influenza A (H1N1), 55 influenza A (H1N2), 105
influenza A (H3N2) and 254 influenza B isolates antigenically. The neuraminidase
typing for one 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).
Netherlands: No further updates
have been found for the outbreak of highly pathogenic avian influenza A (H7N7
HPAI) in chickens which began during February 2003 in the Netherlands.
Between February and April of 2003, this outbreak had spread to Belgium
and Germany, to swine herds in the Netherlands, and to humans.
The 83 confirmed cases of human H7N7 in the Netherlands included one
death, 79 with conjunctivitis and 13 with mild ILI.
The WHO Influenza Collaborating Centers are to begin production of a
reagent kit to identify H7N7 viruses. More
information about this outbreak of H7N7 HPAI can be found at:
Asia: An avian flu virus
strain, influenza A (H5N1), was recovered from two influenza cases in Hong Kong
earlier this year. 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.