(CNN) Flu activity remains high across the nation, and there's a second wave of severe infections striking some states.

There were as many as 26.3 million flu illnesses , 12.4 million medical visits and 347,000 flu hospitalizations between October 1 and March 2, according to the weekly flu report released Friday by the US Centers for Disease Control and Prevention.

"We're still having flu. And we're still seeing a steady stream of patients who are being admitted to hospital with influenza," said Dr. William Schaffner, medical director of the National Foundation for Infectious Diseases.

Nine additional children died of flu-related causes during the week ending March 2, bringing the total to 64 for the season. However, not all flu-related deaths are detected or reported, so the CDC believes the actual number of deaths to be higher.

For adults, flu deaths are estimated based on pneumonia and other illnesses related to flu. The proportion of deaths attributed to pneumonia and flu during the week ending February 23 was 7.5%, slightly higher than the usual threshold of 7.3% for this time of year, the CDC said, based on data from the National Center for Health Statistics.

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