Flu Cases on the Rise in U.S.

CDC Report Shows Influenza Is Present in All 50 States

Medically Reviewed by Laura J. Martin, MD on February 17, 2011

Feb. 17, 2011 -- Flu activity was relatively low in most of the U.S. from October through early December, but it has increased and is now widespread in most states, the CDC says.

The CDC’s Morbidity and Mortality Weekly Report for Feb. 18 says the flu is now present now in all 50 states and the District of Columbia.

The percentage of overall deaths attributed to pneumonia or influenza first exceeded the epidemic threshold in late January, the CDC says. And the number of pediatric influenza-associated deaths reported to officials has tripled from 10 before Jan. 16 to 30 since then.

Flu continues to be associated with a large number of outpatient doctor’s visits, hospitalizations, and deaths, especially among people at high risk.

The CDC says flu activity has continued to increase in early February. Influenza strains that have been identified include influenza B, 2009 influenza A (H1N1), and influenza A (H3N2).

Several Flu Strains Causing Sickness

The CDC says that between early October 2010 and Feb. 5, 2011, laboratories worldwide tested 116,255 people for influenza viruses and 22,641 had one of the strains, or about 19.5% of the total.

Of those:

  • 73% or 16,494 were influenza A viruses, and 27% or 6,145 were influenza B viruses.
  • Of 11,094 influenza A viruses that were subtyped, 7,845 or 71% were influenza A (H3) viruses, and 3,249 or 29% were 2009 influenza A (HI) viruses.

Flu activity for the week ending Feb. 5 was widespread in 37 states and regional in nine states. Washington, D.C., reported local activity, and four states plus Puerto Rico, Guam, and the U.S. Virgin Islands reported sporadic activity.

The cumulative hospitalization rate per 100,000 people for the Oct. 3, 2010-Feb. 5, 2011 period was:

  • 14.5 among kids up to age 4
  • 2.5 among children 5-17
  • 3.5 among adults 18-49
  • 6.3 among adults 50-64
  • 18.8 among adults 65 and older

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%.

Pediatric Deaths Reported

As of Feb. 5, the CDC says 30 flu-related pediatric deaths were reported from 18 states. During the pandemic of 2009, the CDC says 329 pediatric deaths were reported between April 15, 2009, and Jan. 23, 2010.

Before the pandemic, 65 pediatric deaths due to flu were reported in the 2008-2009 season, 88 in the 2007-2008 period, and 77 in 2006-2007.

The CDC points out that flu activity typically peaks in February but says this can occur as late as May, so vaccination would still be worthwhile.