Although September typically marks the beginning of the annual flu season, January and February are often the most severe months. This year a particularly nasty flu season could hang around until May, U.S. health officials warn.
Three strains of influenza viruses — influenza A (H3N2), 2009 influenza A (H1N1) and influenza B viruses — have been especially punishing in terms of the number of people infected and the severity of symptoms, the United States Centers for Disease Control and Prevention (CDC) reported.
“This is the H1N1 virus that emerged in 2009 to cause a pandemic. H1N1 viruses have continued to circulate among people since that time, but this is the first season that the virus has circulated at high levels since the pandemic,” according to the CDC weekly flu report.
Forty states now report widespread influenza activity for the week of January 5-11, 2014, the latest figures available.
This is an increase from the previous week when 35 states reported widespread activity. Guam and nine other states report regional flu cases. The District of Columbia and Puerto Rico report local flu activity for the same period.
The flu has been particularly life-threatening for two groups: the very young and the elderly.
For children, it was one of the deadliest weeks yet, with nine more dying from flu-related illness, bringing the season’s pediatric death toll to 20 in 13 states.
Children 5 years of age and younger are at especially high risk of severe complications.
In typical years the highest proportion of influenza-associated hospitalizations occur in people 65 and older, and children younger than 5 years of age. This year has been an exception.
Of the 3,745 influenza-associated hospitalizations that have been reported this season, 61 percent have been in people 18-64 years old. The same pattern of more hospitalizations among younger people occurred during the 2009 H1N1 pandemic, according to the CDC.