The Centers for Disease Control and Prevention said flu cases had waned in recent weeks but that the cold-weather virus could still make a comeback before the end of the season.
"It's not surprising," Dr. Thomas Frieden, director of the CDC, said in teleconference last Friday. "Influenza ebbs and flows during the flu season. The only thing predictable about the flu is that it is unpredictable."
Flu cases have been recorded in 47 states so far this year. But only 24 states reported high flu activity levels in the first week of January compared with the 29 that reported high flu activity in the last week of December. Another 16 states reported moderate levels of activity during the same week in January, while five reported low levels and one reported minimal levels.
Hospitals in many areas of the country have said they've been overwhelmed by this year's epidemic, which came on hard, fast and early. The disease prompted a public health emergency in Boston, where health officials said last week that 700 people had been diagnosed with the infectious respiratory disease, and 18 had died from flu-related complications in the state.
In New York, Gov. Andrew Cuomo declared a public health emergency at the end of last week, allowing pharmacists to administer vaccines to patients six months to 18 years old. The executive order suspended a state law that limited immunizations to people older than 18.
The CDC urged all Americans to get flu shots if they hadn't already. Heightened demand has caused some providers to run out of the vaccine, but officials said there was still plenty to go around but encouraged people to call ahead before heading out to a local clinic to get immunized.
Dr. Richard Besser, ABC News' chief health and medical correspondent, said this could be the worst flu epidemic in a decade, but that it's not too late to protect yourself from the virus.
"You have to think about an anti-viral, especially if you're elderly, a young child, a pregnant woman," Besser said. To raise public awareness about flu prevention and treatment, Besser will host a one hour "tweet chat" on Twitter today from 1-2 p.m. ET. To participate, sign into Twitter and click here for the hashtag. Follow the conversation or jump in with comments and questions of your own.
Medical experts from the CDC, National Institutes of Health, the Mayo Clinic and the Boston Children's Hospital Healthmap.org project will join Besser on the chat to answer questions and offer advice.