The CDC received multiple reports of influenza A H1N1 pdm09 infection that resulted in hospitalizations, including many that required intensive care unit admission. Some fatalities were reported as a result of the pH1N1-associated hospitalizations. During the 2009 pandemic, pH1N1 caused more illness in children and young adults than in older children.
The CDC said the pH1N1 strain has been the predominant circulating virus so far during the 2013-14 influenza season. The agency said that if pH1N1 continues to circulate widely, illness may disproportionately affect young and middle-aged adults.
According to the report, while most individuals with severe illness had risk factors for influenza-associated complications, such as morbid obesity and pregnancy, several have not.
The CDC recommends that anyone six months and older receive an annual influenza vaccine and said it is the best tool to prevent influenza and its complications. Antiviral drugs like oseltamivir and zanamivir serve as a second line of defense to reduce morbidity and mortality.
According to the CDC, an estimated 380,000 influenza-associated hospitalizations occurred during the 2012-13 influenza season in the U.S.