Four confirmed cases of influenza and two hospitalizations were reported during the week ending Dec. 29, according to South Dakota Department of Health surveillance data.

Influenza activity in the state is sporadic, with isolated cases of influenza confirmed by a laboratory. So far during this season, 15 cases and 122 positive rapid antigen flu tests have been confirmed. Eight people have been hospitalized this season, but no deaths have been reported.

During the 2006-07 flu season, six deaths and 132 hospitalizations were reported.

Though the season varies from year to year, typically, South Dakota's flu season doesn't peak until February. Health officials say it isn't too late for people to be immunized. Young children, older people and those with certain health conditions such as heart and lung ailments are at particularly high risk and should get the shot.

Influenza is a contagious respiratory illness caused by a virus that can cause mild to severe illness and sometimes death. Symptoms can include fever, aches, extreme fatigue, a dry cough, a runny or stuffed-up nose and sore throat.