Influenza activity increased the week ending Jan. 6, with all but one state reporting widespread flu activity, according to the CDC's most recent update on the 2017-18 flu season published Friday.
During a media call Friday, CDC Director Brenda Fitzgerald, MD, and Daniel Jernigan, MD, director of the CDC's influenza division, said flu season is likely at its peak, but cautioned that it will take several more weeks before flu activity slows down.
Here are five things to know.
1. Every state in the continental U.S. reported widespread influenza activity for the week ending Jan. 6. Hawaii and Guam reported regional flu activity; Washington, D.C., reported local influenza; U.S. Virgin Islands reported sporadic activity; and Puerto Rico did not report flu activity to the CDC for the week.
"Flu is everywhere in the U.S. right now," Dr. Jernigan said. "There's lots of flu in lots of places."
2. The most frequently identified virus type in positive specimens continued to be influenza A, with a majority of these cases — 89.9 percent — attributable to the H3N2 The H3N2 strain is associated with more severe illnesses in the elderly and young children.
3. Flu seasons in which H3N2 is the dominant strain tend to be more severe. Of the two seasons in the last 13 years considered high in severity — 2003-04 and 2014-15 — H3N2 was the dominant strain, according to Dr. Jernigan. The CDC official referred to the nation's current flu season as severe, but said the level of severity is still unclear. The CDC does not expect this season to reach the level of severity seen in 2014-15, according to Dr. Jemigan.
4. The CDC reported seven additional pediatric flu deaths for the week ending Jan. 6, increasing the total number of flu-related pediatric deaths to 20 for the current flu season. The agency tallied a total of 110 such deaths for last year's flu season.
5. Jernigan said the CDC anticipates the H3N2 component of this year's influenza vaccine to be about 30 percent effective with overall vaccine effectiveness rates at about 40 percent.
"While our flu vaccines are far from perfect, they are the best way to prevent the flu, and it's not too late to get one," Dr. Fitzgerald said during the media call.
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