Flu activity in the United States rose steadily again last week, with the 2009 H1N1 virus predominating in most of the country except for the Southeast, the US Centers for Disease Control and Prevention (CDC) said today in its latest update.
Officials received reports of four more pediatric flu deaths, raising the season's total so far to 11. The percentage of respiratory samples that tested positive for flu at clinical labs last week was 15.6%, of which 96.7% was influenza A and 3.3% influenza B. Of subtyped influenza viruses at public health labs, 89.2% were 2009 H1N1 and 10.8% were H3N2.
However, the CDC said in an accompanying situation report that in the most recent 4 weeks, H3N2 has predominated in the southeastern United States.
Markers show flu expanding in most of US
All but 1 of the CDC's 10 regions are at or above their specific baselines. The only one that isn't is the northwest region, which includes Alaska, Idaho, Oregon, and Washington.
Nationally, the percentage of clinic visits for flulike illness rose from 2.7% to 3.3% last week, a measure that has been above the seasonal baseline for five consecutive weeks. New York City and nine states are reporting high flulike illness activity, up from just two the previous week. The states are Alabama, Colorado, Georgia, Kentucky, Louisiana, Maryland, New Jersey, New Mexico, and South Carolina.
Guam and 11 states are reporting widespread flu activity, up from 6 states the previous week. States with widespread activity are Arizona, California, Connecticut, Delaware, Florida, Georgia, Massachusetts, Nebraska, New Mexico, New York, and North Carolina.
The overall hospitalization rate was 3.6 per 100,000 population, an increase from 2.9 reported the week before. The highest rates are among children up to age 4, followed by adults age 65 and older, and adults ages 50 to 64. Most involved influenza A, and, of subtyped influenza A viruses from hospitalized patients, 77.4% were 2009 H1N1.
The CDC has said that 2009 H1N1 has been associated with a significant burden and severe illness in young children.
The level of deaths from pneumonia and flu are still below the seasonal baseline, an indicator that typically lags other flu markers.
Regarding the four pediatric flu deaths, one child died the first week of December and the other three died during the weeks ending Dec 15 and 22. Three of the deaths were linked to the 2009 H1N1 virus, and the fourth involved unsubtyped influenza A.
Dec 28 CDC FluView report
Dec 28 CDC situation update