US flu activity higher than national baseline

The number of outpatient visits for influenza-like illness so far this season is above the national baseline, according to the CDC’s FluView.

This year’s influenza season is the earliest regular influenza season seen since the 2003-2004 season, CDC director Thomas Frieden, MD, said during a media briefing.

Thomas Frieden

“That was an early and severe flu year and although flu is unpredictable, the early nature of this year’s season, as well as the specific strains we are seeing suggest that this could be a bad flu year,” Frieden said.

According to FluView for week 52, which ended Dec. 29, influenza activity has increased in the United States. There were 9,363 specimens tested and reported, of which 31.6% were positive for influenza. In addition, the proportion of outpatient visits for influenza-like illness was 5.6%; the national baseline is 2.2%.

Twenty-nine states and New York City reported high influenza-like activity and nine out of 10 regions reported influenza-like illness above the region-specific baseline levels. The proportion of deaths that were attributed to pneumonia and influenza was below the epidemic threshold. There have been, however, a cumulative total of 18 pediatric influenza-related deaths this season.

Cumulatively, the number of influenza cases this season include 194 cases of 2009 H1N1, 10,612 cases of influenza A (H3N2), 4,708 cases of influenza B and 5,621 cases of influenza A in which subtyping was not performed.

Frieden said that the strains identified thus far appear to be a good match for this year’s vaccine. The primary strains are influenza A, predominantly H3N2. Frieden also said that historically, years that have a predominant H3 strain tend to be worse years.

“Anyone who has not already been vaccinated should do so now,” Joseph Bresee, MD, FAAP, chief of the Epidemiology and Prevention Branch at CDC’s Influenza Division, said in a press release. “It’s important to remember that people who have severe influenza illness, or who are at high risk for serious influenza-related complications, should get treated with influenza antiviral medications if they get flu symptoms regardless of whether or not they got vaccinated. Also, you don’t need to wait for a positive laboratory test to start taking antivirals.”