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Summary of 2005-2006
influenza season
Season summary
Lab surveillance
Influenza-like illness sentinel surveillance
Season
summary of flu activity
Arizona's influenza
activity peaked early in the 2005-2006 season, with the highest number of cases
seen during the last week of December. All
15 counties reported positive flu labs and there were two influenza-associated
deaths among Arizona children this season.
The Arizona season began with influenza A as the
predominant strain in circulation, but influenza B became the primary strain
after February.
Lab surveillance
Labs
have been required to report positive influenza tests to ADHS since 2004.
A total of 5,197 lab-confirmed cases of influenza were reported during
the 2005-2006 season. Of these, 4,018 cases were influenza A (769 confirmed by
culture or PCR), 340 cases were influenza B (91 confirmed by culture or PCR),
and 839 cases were non-specific rapid tests.
Viral
isolation, or culture, is currently the "gold standard" for diagnosis
of influenza virus infections. Subsequent
laboratory testing of influenza culture-positive specimens can be used to
identify the influenza A subtype. This subtyping analysis is performed on
a subset of lab-confirmed cases. Polymerase chain reaction (PCR) can also
be used to identify influenza B and the hemagglutinin (H) component of influenza
A. Of the 769 culture-
or PCR-confirmed influenza A, 68
were H3N2, 307 were
H3 with no N subtyping available, and the others were not subtyped.
More cases were reported from the 1-19 year age group (32%) than any other,
but the incidence rate of reported cases was highest among infants less than 1
year of age.
Influenza-like illness (ILI)
surveillance from sentinel providers
Influenza-like
illness (ILI) surveillance measures the proportion of patient visits to sentinel
providers for ILI out of the total visits each week. A distinct peak in
ILI was observed in the latter half of December, mirroring the peak in
laboratory-confirmed influenza.
ILI
data for May are based on reports from <50% of providers.
National
information about the 2005-2006 influenza season can be found at the CDC
influenza website.
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