Flu Season Has Started Early

The 2017-2018 influenza season appears to have begun early, with widespread influenza activity already affecting several states, according to a recent report from the Centers for Disease Control and Prevention (CDC). As a result, this year’s influenza season may peak even sooner than January or February.

Currently, the most widespread influenza activity is present in Georgia, Louisiana, Massachusetts, and Oklahoma, while 10 states including Connecticut, Maine, New Hampshire, and Washington are affected by regional flu activity.

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The CDC reported that, as of November 25, 2017, the proportion of outpatient visits for influenza-like illness was 2.3%, surpassing the national baseline of 2.2%. The most frequently reported type of influenza virus during week 47 (November 19 to 25) was influenza A, including A(H3N2) virus and A(H1N1)pdm09 virus.

A reported 566 laboratory-confirmed hospitalizations due to influenza had occurred between October 1 and November 25, 2017. Of these hospitalizations, 484 (85.5%) were caused by influenza A virus, while 80 (14.1%) were due to influenza B virus and 2 (0.4%) due to influenza A and B virus co-infection.

Hospitalizations during this time frame occurred most frequently among adults aged 65 years or older, followed by adults aged 50 to 64 years and children aged 0 to 4 years.

Although many people in the United States often opt to receive the influenza vaccine, this year’s vaccine may not be fully effective, especially against H3 viruses. The H3N2 component in this year’s vaccine is identical to that of last year, which was found to decrease recipients’ risk of infection by only about 34%.

—Christina Vogt


Weekly U.S. influenza surveillance report: 2017-2018 influenza season week 47 ending November 25, 2017. Centers for Disease Control and Prevention. November 25, 2017. Accessed December 4, 2017.