Flu Activity Widespread in the United States
According to the Centers for Disease and Control (CDC), flu activity in the United States was relatively low from October through early December, but has spread to all 50 states and activity is widespread in approximately 75% of states.
The CDC’s Morbidity and Mortality Weekly Report for Feb. 18 reports Influenza B, 2009 influenza A (H1N1), and influenza A (H3N2) viruses all have been identified thus far this influenza season, and most viruses in circulation are antigenically similar to strains included in the 2010--11 vaccine.
The CDC MMWR reports the percentage of overall deaths attributed to pneumonia or the flu exceeded the epidemic threshold in the last week of January. Prior to January 16, 2011, there were 10 pediatric flu-associated deaths (2010-2011 season). This number tripled in the past month with 30 reported deaths since January 16, 2011.
In 2010-11, influenza continues to be associated with a substantial number of out-patient visits, hospitalizations, and deaths, particularly among high risk persons.
Based on EIP surveillance data, those hospitalized (per 100,000 population) for October 3, 2010--February 5, 2011, were most likely to be children aged 1-4 years (14.5) or elderly adults over 65 years (18.8). The cumulative incidence for all age groups since October 3, 2010, was 6.3 per 100,000.
The CDC says pneumonia and influenza were reported as underlying causes of death for 8% of all fatalities for the week ending Feb. 5, reaching the epidemic threshold of 7.97%.
The CDC reports that flu surveillance testing done on 116,255 respiratory specimens for influenza viruses from October 3, 2010--February 5, 2011 resulted in 22,641 (19.5%) positive tests. Of these, 16,496 (73%) were influenza A viruses, and 6,145 (27%) were influenza B viruses. Subtyping of the influenza A viruses noted that 71% were influenza A (H3) viruses and 29% were 2009 influenza A (H1) viruses.
The CDC points out that flu activity typically peaks in February but says this can occur as late as May, so it is not too late to get a flu vaccination. Annual vaccination is the most effective method to prevent influenza and its complications. All persons older than 6 months of age who have not yet been vaccinated this season should talk to their healthcare providers about getting vaccinated.