Flu season started early this winter, and includes a strain that tends to make people sicker. Health officials have forecast a potentially bad flu season, following last year's unusually mild one.
The latest numbers, however, hint that the flu season may already have peaked in some spots.
Flu was widespread in 47 states last week, up from 41 the week before, the Centers for Disease Control and Prevention said on Friday. Many cases may be mild. The only states without widespread flu are California, Mississippi and Hawaii.
The hardest hit states dropped to 24 from 29. Those are states where large numbers of people have been treated for flu-like illness.
Those with less activity include Florida, Arkansas and South Carolina in South, the first region hit in the current flu season.
Nationally, 20 children have died from the flu. There is no running tally of adult deaths, but the CDC estimates that the flu kills about 24,000 people in an average year.
Flu vaccinations are recommended for everyone 6 months or older. Health officials are still recommending vaccinations, even in areas with widespread flu reports.
Nearly 130 million doses of flu vaccine were distributed this year, and at least 112 million have been used, according to CDC officials.
Vaccine is still available, but supplies may have run low in some locations, health officials say.
Also on Friday, CDC officials said a recent study of more than 1,100 people has concluded the current flu vaccine is 62 percent effective. That's in line with how effective the vaccine has been in other years.
The flu vaccine is reformulated each year, and officials say this year's version is a good match to the viruses going around.
Flu usually peaks in midwinter. Symptoms can include fever, cough, runny nose, head and body aches and fatigue. Some people also suffer vomiting and diarrhea, and some develop pneumonia or other severe complications.
Most people with flu have a mild illness. But people with severe symptoms should see a doctor. They may be given antiviral drugs or other medications to ease symptoms.