Nebraska ? Midway through the month when influenza typically peaks, health officials were monitoring four hospitalized Nebraska children, while three North Carolina schools remained closed over widespread symptoms of the illness.

And in Oklahoma, one school district reported 350 students out sick Friday, though no schools were closed, authorities said.

Still, a federal health official called this season relatively mild so far.

Around the country, at least nine children have died of flu, and six other child deaths have been tentatively linked to flu since Feb. 3, said Curtis Allen, a spokesman for the Centers for Disease Control and Prevention.

Last year, 47 children younger than 18 died from influenza. In 2003-04, the worst recent flu season, 153 children died.