Minnesota has recorded its first death of the 2014 influenza season, as state authorities reported a sharp jump in flu cases reported by "sentinel" clinics across the state.

The victim was a child but was not identified Thursday by the Minnesota Department of Health. The department said 18 new patients were hospitalized with flu symptoms last week, about average for this stage of the season, and eight school districts reported new flu outbreaks.

Influenza's severity varies widely from one year to another, with a national death toll ranging from 3,300 to 49,000 annually.

Federal health officials said Thursday that flu vaccine might be less effective than normal this year, because of a shifting composition of flu strains, but in guidance to clinics and patients, Minnesota officials said a flu shot still offers valuable protection. Even at 60 percent effectiveness, flu vaccine is better than zero protection, the Health Department said.

Influenza typically emerges in late fall and peaks between December and February. Flu symptoms include fever, cough, sore throat and body aches. Most patients recover within a few days, but flu can cause severe complications, especially in infants, the elderly and people with chronic medical conditions such as asthma and diabetes.