The Centers for Disease Control and Prevention in Atlanta, which tracks flu-like illness, said for the week ending March 3, doctor visits for flu-like illness stayed below the baseline, but levels were above regional baselines for much of the Midwest.
The percentage of respiratory specimens that tested positive for influenza rose to 21.3 percent, compared to 18.4 percent of the previous week, the CDC said.
The rate of hospitalizations for laboratory-tested confirmed influenza reached 2.1 per 100,000 people last week, an increase of 36 percent from the previous week, although levels are still lower than expected for this time of the year, the CDC said.
Almost 90 percent of the hospitalizations this flu season have involved influenza A strains and of 246 type A isolates that were sub-typed, 185 were H3N2 and 61 were 2009 H1N1, the Centers for Infectious Disease Research & Policy at the University of Minnesota reported.
Kansas, Missouri and Oklahoma reported high flu-like illness activity. California, Colorado, Illinois, Kansas, Missouri, Nevada, New Jersey, Oklahoma and Virginia report wide geographic spread of the flu.