Weekly Report: Influenza Summary Update
Week 43, ending October 28, 2006
Synopsis:
During week 43 (October 22 October 28, 2006)*, a low level of influenza activity
was reported in the United States. Six (0.6%) specimens tested by U.S. World
Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance
System (NREVSS) collaborating laboratories were positive for influenza. The
proportion of patient visits to sentinel providers for influenza-like illness
(ILI) and the proportion of deaths attributed to pneumonia and influenza were
below baseline levels. Two states reported local influenza activity; ten states
reported sporadic influenza activity; 36 states, New York City, and the District
of Columbia reported no influenza activity; and two states did not report.
Laboratory Surveillance*:
During week 43, WHO and NREVSS laboratories reported 1,054 specimens tested
for influenza viruses, six of which were positive: three influenza A (H1) viruses,
two influenza A viruses that were not subtyped, and one influenza B virus.
Since October 1, 2006, WHO and NREVSS laboratories have tested a total of 5,715
specimens for influenza viruses and 49 (0.9%) were positive. Among the 49 influenza
viruses, 34 (69.4%) were influenza A viruses and 15 (30.6%) were influenza B
viruses. Thirty (88.2%) of the 34 influenza A viruses have been subtyped: 23
(76.7%) were influenza A (H1) viruses and 7 (23.3%) were influenza A (H3) viruses.
Thirteen states from six of the nine surveillance regions** have reported laboratory
confirmed influenza this season.
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Antigenic Characterization:
Since October 1, 2006, CDC has antigenically characterized one influenza virus
collected by U.S. laboratories. The influenza A (H1) virus was characterized
as A/New Caledonia/20/99 -like, which is the influenza A (H1) component recommended
for the 2006-07 influenza vaccine.
Pneumonia and Influenza Mortality Surveillance:
During week 43, 6.14% of all deaths were reported as due to pneumonia or influenza.
This percentage is below the epidemic threshold of 6.56% for week 43.
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Influenza-Associated Pediatric Mortality:
No influenza-associated pediatric deaths were reported for week 43.
Influenza-Associated Pediatric Hospitalizations
Laboratory-confirmed influenza-associated pediatric hospitalizations are monitored
in two population-based surveillance networks: the Emerging Infections
Program (EIP) and the New Vaccine Surveillance Network (NVSN). No influenza-associated
pediatric hospitalizations have been reported from the EIP. NVSN estimated rates
of hospitalization for influenza will be reported every 2 weeks, beginning December
2006.
Influenza-like Illness Surveillance*:
During week 43, 1.2%*** of patient visits to U.S. sentinel providers were due
to ILI. This percentage is less than the national baseline**** of 2.1%. On a
regional level**, the percentage of visits for ILI ranged from 0.4% to 2.1%
with no regions above their region-specific baseline****.
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Influenza Activity as Assessed by State and Territorial Epidemiologists*:
During week 43, the following influenza activity was reported:
Local activity was reported by two states (Alabama and Louisiana).
Sporadic activity was reported by ten states (California, Connecticut, Florida,
Hawaii, Indiana, Massachusetts, Mississippi, New York, Pennsylvania, and Texas).
No influenza activity was reported by New York City, the District of Columbia
and 36 states.
No reports were received from two states.
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