MINNEAPOLIS, Feb. 3 (UPI) -- U.S. flu activity increased slightly last week and the Midwest showed higher evidence of influenza but flu activity is low nationwide, health officials said.
The Centers for Disease Control and Prevention said doctors' visits for flu-like illness remained below the national baseline but the percentage of respiratory specimens testing positive for flu rose from 5.6 percent the previous week to 7.2 percent the week ending Jan. 28.
The number of deaths from pneumonia and flu dropped below the epidemic threshold, after exceeding it during the previous week for the first time this flu season, but no pediatric flu deaths were reported, keeping the total so far this year at one, the Centers for Infectious Disease Research & Policy at the University of Minnesota reported.
Although flu activity is still low, the CDC reported regional variations. For example, very few specimens in the mid-Atlantic region -- 1.4 percent -- tested positive for flu. However, 17.4 percent of specimens in the Midwest showed evidence of influenza.
The CDC said it is seeing regional differences in the types of flu strains that are circulating. The 2009 H1N1 virus has become the dominant strain in the south central region of the country and is steadily increasing in southwestern states, the CIDRP reported.
Overall, the H3N2 seasonal flu virus is dominating, though influenza B is the dominant strain in China, while Mexico is seeing mostly the 2009 H1N1 virus, the report said.
