Influenza activity in the United States is continuing a slow decline that first became apparent 2 weeks ago, with most indicators down again last week, the Centers for Disease Control and Prevention (CDC) reported today.
Among the signs were decreases in positive test results, the number of states with high activity, and deaths in children.
The CDC said 19.6% of 8,282 respiratory samples tested positive for flu, compared with 21.1% of 9,514 samples a week earlier. The share of medical visits due to influenza-like illness (ILI) was 3.2%, down a hair from 3.3% the week before, though still well above the national baseline of 2.0%.
High activity in seven states
Just seven states, most of them south-central, reported high flu activity, down from 10 the week before. The number of states with moderate activity stayed the same at 12.
In terms of geographic extent, 29 states had widespread flu activity last week, versus 38 the previous week. Nineteen states still had regional activity, the next geographic category, compared with 10 a week earlier.
Three flu-related pediatric deaths were reported last week, which was six fewer than the week before. The latest deaths raised the seasonal total to 40. The three cases involved influenza viruses that were not subtyped.
The share of deaths attributed to flu and pneumonia, an indicator that typically lags behind most others, sank to 8.6% last week, from 8.8% the previous week. But the number remained well above the epidemic threshold of 7.3%, the CDC said.
The CDC's surveillance system for flu-related hospitalizations, which covers 70 counties in 10 states, recorded 587 cases last week, down from 879 the preceding week. The season's total reached 6,081, which indicates a rate of 22.5 hospitalizations per 100,000 population.
In a related development, the California Department of Public Health (CDPH) reported today that 56 flu-related deaths were reported in the state in the past week. That raises the season total to 202, close to double the 106 deaths reported during the previous flu season. Officials said another 41 deaths are still under investigation.
The CDC said 2009 H1N1 viruses continued to be overwhelmingly predominant among flu isolates that were subtyped, with only a few H3N2 and type B isolates found. Two more isolates, both H1N1, with markers of resistance to antiviral drugs (neuraminidase inhibitors) were found. Those brought the seasonal total to 23, all of them H1N1 viruses.
Activity still rising in Europe
This week's update from the European Centre for Disease Prevention and Control (ECDC) suggests that flu activity is continuing to increase in Europe. The agency said 17 countries and the United Kingdom (Scotland and Wales) reported increasing ILI activity.
Greece was the only country reporting high-intensity activity, but six others—Bulgaria, Finland, France, Luxembourg, Malta, and Spain—reported medium activity, up from four countries a week earlier. The other 22 countries reported low intensity.
The proportion of sentinel respiratory specimens testing positive for flu has dropped in the past 2 weeks, but eight countries reported geographically widespread flu activity last week, an increase from the week before, the ECDC said.
H3N2 and 2009 H1N1 viruses are both circulating in Europe, with the balance varying by country, the agency reported.
CDC FluView report
Feb 7 CDPH press release
Feb 7 ECDC report