Influenza-like illness (ILI) activity jumped from 3.3% to 4.1% last week, an indicator of increasing flu activity across much of the country, the US Centers for Disease Control and Prevention (CDC) said today in its latest FluView update.
"The increase in the percentage of patient visits for ILI may be influenced in part by a reduction in routine healthcare visits during the winter holidays, as has occurred during previous seasons," the CDC said.
The national baseline ILI rate is 2.2%, and the CDC defines ILI as fever (temperature of 100°F or greater) and cough and/or sore throat.
All 10 regions surveyed by the CDC reported elevated flu activity, with 24 states reporting widespread activity.
Two weeks ago, only 9 states reported high ILI activity. Last week, New York City and 19 states (Alabama, Arizona, Colorado, Georgia, Illinois, Indiana, Kansas, Kentucky, Louisiana, Massachusetts, Mississippi, Nevada, New Jersey, New Mexico, Oklahoma, South Carolina, Texas, Utah, and Virginia) experienced high ILI activity, while 9 states (Arkansas, California, Michigan, Missouri, New York, North Carolina, Pennsylvania, Rhode Island, and Vermont) reported moderate ILI activity.
Two new pediatric deaths
The CDC also recorded two pediatric influenza-related deaths last week, raising this season's total to 13. Both deaths were associated with influenza A 2009 H1N1 viruses.
The overall hospitalization rate was 5.4 per 100,000 population. Children ages 0 to 4 years had the highest rate of hospitalization (14.5 per 100,000 population), followed by adults 65 and older (11.9 per 100,000 population) and adults ages 50 to 64 years old (6.2 per 100,000 population).
Almost 90% (89.4%) of hospitalizations were associated with influenza A virus. Among those with influenza A subtype information, 272 (79.3%) were H1N1 and 71 (20.7%) were H3N2.
The percentage of respiratory samples that tested positive for flu at clinical labs last week was 13.1%, of which 97.1% was influenza A and 2.9% influenza B. Of subtyped influenza A viruses, 89.4% were H1N1 and 10.6% were H3N2.
The CDC recommended that anyone 6 months of age or older who has not yet received the flu vaccine do so as soon possible.
Jan 4 CDC FluView