The overall flu picture didn't change much last week, with activity remaining elevated and the H3N2 virus pushing the 2009 H1N1 strain out of its dominant spot in several parts of the country, the US Centers for Disease Control and Prevention (CDC) said today in its weekly update.
Overall, severity markers such as hospitalizations and deaths continue increase, as they typically do later in the flu season, but the levels are substantially lower than last season, which was severe.
Lab indicator details
The percentage of respiratory specimens that tested positive for flu slightly increased last week, from 25.9% to 26.1%, but clinic visits for flulike illness dropped a bit, from 5% to 4.7%, but remained well above the national baseline of 2.2%.
For the second week in a row, H3N2 viruses were reported more frequently than 2009 H1N1, which had been predominant across the season.
So far, little influenza B is circulating. At clinical labs last week, influenza A accounted 97.2% of specimens that were positive for flu. And at public health labs, of subtyped influenza A viruses last week, 62% were H3N2 and 38% were 2009 H1N1.
Much high, widespread activity
The number of states reporting high flulike illness activity, another clinic visit indicator, decreased from 33 states plus New York City to 32 states, with the high-activity areas located mainly in the bottom half of the nation and in Alaska.
Areas reporting widespread flu last week decreased slightly from Puerto Rico and 49 states to Puerto Rico and 48 states, the CDC said.
Hospitalizations and deaths
Hospitalizations for flu rose to 36.6 per 100,000 population, with the highest rates in seniors, followed by children younger than 5 years and adults ages 50 to 64.
For comparison, the hospitalization rate is less than half of what it was at this point last season.
Nine more pediatric flu deaths were reported to the CDC last week, eight of which occurred during the current flu season and one from the 2015-16 season, raising the total to 64 for this season.
Of the 8 new deaths, 4 involved 2009 H1N1, 1 H3N2, 1 influenza B, and 2 from unsubtyped influenza A. The child from the earlier season died from an unsubtyped influenza A infection, the CDC said.
Overall deaths from pneumonia and flu, which typically lag other seasonal indicators, rose above the epidemic threshold last week, reaching 7.5%.
The CDC said it expects flu activity to stay elevated for several more weeks and added that getting vaccinated is the best way to protect against flu and its potentially serious complications.
See also:
Mar 8 CDC FluView report
Mar 8 CDC situation report
