CDC reports significant rise in flu activity

The U.S. Centers for Disease Control and Prevention reported a substantial rise in flu activity in the U.S. last week, reaching the national baseline at the earliest point in the season since 2003-2004.

The percentage of doctor visits for flu-like illness grew from 1.6 percent the previous week to the national baseline of 2.2 percent last week. The rise in flu activity is mostly from southeastern and south central states, though there is wide variation in the regional percentages of respiratory samples testing positive for flu, ranging from 3.8 percent to 20.6 percent, CIDRAP News reports.

The percentage of deaths from flu and pneumonia rose to 6.3 percent last week, putting it shy of the 6.7 percent epidemic threshold.

South Carolina, New York, Mississippi and Alaska reported widespread geographic spread of flu last week. Additionally, seven states reported regional spread and 19 states reported local activity. Only eight states reported local activity the prior week.

All seasonal flu strains are in circulation and H3N2 is responsible for approximately 35 percent of the sub-typed influenza viruses. The 2012-2013 vaccine matched up with both of the 2009 H1N1 viruses and all 90 of the H3N2 viruses circulating. Approximately 70.8 percent of the influenza B samples tested matched the virus included in the most recent vaccine, CIDRAP News reports.

The CDC also reported a new case of variant H3N2 in Iowa. The patient had no contact with swine or other livestock prior to becoming sick and has since recovered. The CDC reports 311 cases of H3N2v since July.