To determine clinical and epidemiologic differences
between influenza caused by different virus types and subtypes,
we identified patients and tested specimens. Patients
were children and adults hospitalized with confirmed influenza
and severe acute respiratory illness (SARI) identified
through active, prospective, hospital-based surveillance
from 2009–2012 in South Africa. Respiratory specimens
were tested, typed, and subtyped for influenza virus by
PCR. Of 16,005 SARI patients tested, 1,239 (8%) were positive
for influenza virus. Patient age and co-infections varied
according to virus type and subtype, but disease severity
did not. Case-patients with influenza B were more likely
than patients with influenza A to be HIV infected. A higher
proportion of case-patients infected during the first wave of
the 2009 influenza pandemic were 5–24 years of age (19%)
than were patients infected during the second wave (9%).
Although clinical differences exist, treatment recommendations
do not differ according to subtype; prevention through
vaccination is recommended.
This information has been presented at Options for the Control
of Influenza VIII, Cape Town, South Africa, September 5–9, 2013.