Federal health officials say the flu season is winding down, and it's turning out to be one of the mildest in years.
The U.S. Centers for Disease Control and Prevention says one possible explanation is that the flu vaccine generally was well-matched to flu viruses this year.
The CDC compares flu seasons by looking at adult deaths from the flu or pneumonia in 122 cities, and at reports of flu-related deaths in children. Both were down significantly this year compared with the 2007-2008 season.
The flu causes an estimated 200,000 hospitalizations and 36,000 deaths annually. The elderly, young children and people with chronic illnesses are at greatest risk. Health officials say vaccination is the best protection.