Flu Deaths hit Epidemic threshold
Medic-ALL (01-04-2015) via MedPage Today's Michael Smith
In the week ended Dec. 20, 6.8% of all deaths observed through the agency's 122 Cities Mortality Reporting System were attributed to pneumonia and flu.
That matches the epidemic threshold for week 51 of 2014, calculated to be significantly higher than a seasonal baseline that uses data for the same week in the previous 5 years, the CDC reported.
At the same time, the rate of influenza-like illness, reported as a percentage of outpatient visits, is elevated both nationwide and in all 10 of the CDC's surveillance regions, the agency said in its weekly flu report.
The proportion of respiratory specimens testing positive for the flu was 28.1% nationally, with a range from 11.3% to 35.9%.
As well, the CDC said, there were four pediatric deaths associated with the flu in week 51, leading to a cumulative total of 15 since the week ending Sept. 28.
Most of the circulating flu is influenza A (H3N2), with a small amount of A (pH1N1) -- the strain responsible for the 2009-2010 pandemic. Only 2.7% of tested samples are influenza B.
Within the 2,023 influenza A samples that were subtyped in week 51, all but one were H3N2, the agency reported.
Flu seasons in which H3N2 virus predominates are usually more severe, and the CDC has previously noted that most of the H3N2 flu that is circulating does not match the H3N2 component of the seasonal vaccine. That continued to be the case in week 51, the agency said.
Those two factors could combine to make this an unusually harsh flu season, but, on the positive side, all of the tested samples, regardless of subtype or strain, were susceptible to neuraminidase inhibitors such as oseltamivir (Tamiflu) and zanamivir (Relenza).