U.S. flu activity low, but rising

ATLANTA, Feb. 18 (UPI) -- The number of U.S. respiratory specimens testing positive for flu rose from 10.5 percent to 15.5 percent last week but flu activity remains low, officials said.

Officials at the Centers for Disease Control and Prevention said for the week ending Feb. 11, widespread influenza activity was reported in only one state -- California -- but regional influenza activity was reported by Alabama, Colorado, Illinois, Iowa, Kansas, Kentucky, Missouri, Nevada, Oklahoma, Texas, Utah and Virginia.

Local influenza activity was reported by Arizona, Connecticut, Georgia, Idaho, Massachusetts, Michigan, Minnesota, Montana, Nebraska, New Hampshire, New Jersey, New York, Pennsylvania, South Carolina, South Dakota, Washington and Wyoming, the CDC said.

Sporadic influenza activity was reported by the District of Columbia, Guam, Alaska, Arkansas, Delaware, Florida, Hawaii, Indiana, Louisiana, Maine, Maryland, Mississippi, New Mexico, North Carolina, North Dakota, Ohio, Oregon, Rhode Island, Tennessee, Vermont, West Virginia and Wisconsin, the health officials said.

The H3N2 virus is still dominating in most parts of the world except for Mexico, which reported 2009 H1N1 virus.

Of the small numbers of viruses that have been antigenically characterized, about 54 percent of the influenza B viruses are from the Yamagata lineage, which is not a component of the seasonal flu vaccine. Globally, the circulating influenza B strains are similar to the vaccine, the Centers for Infectious Disease Research & Policy at the University of Minnesota reported.

It is too early in the season to assess how well the vaccine matches the circulating strains, the CDC said.