H1N1 hitting young and middle-aged adults

Early reports from the 2013-2014 flu season indicate that young and middle-aged adults may be disproportionately affected by the influenza A (H1N1) pdm09 (pH1N1) virus, the CDC recently warned.

In November and December, the CDC received a number of reports of severe respiratory illness in this patient population, many of which resulted in hospitalizations, intensive care unit admission and even some fatalities. Most of the patients with severe illness had risk factors for influenza-associated complications, including pregnancy and morbid obesity, but several did not. Since its emergence in 2009, the pH1N1 virus has been known to cause more illness in younger patients, the CDC noted.

The pH1N1 virus has been the predominant circulating virus so far this flu season. If it continues to circulate widely, flu outbreaks may disproportionately affects young and middle-aged adults, the CDC warned. Flu activity nationally is currently at low levels, but some areas of the United States are already experiencing high activity and activity is expected to increase during the next few weeks. The spectrum of illness in the 2013-2014 season has ranged from mild to severe and is consistent with that of other influenza seasons, the CDC said.

The agency stressed that annual vaccination is recommended for everyone 6 months and older and that antiviral treatment is recommended as early as possible for any patient with confirmed or suspected influenza who is hospitalized; has severe, complicated, or progressive illness; or is at higher risk for complications.