Flu activity remains high across the nation, and there's a second wave of severe infections striking some states.
There were as many as 26.3 million flu illnesses , 12.4 million medical visits and 347,000 flu hospitalizations between October 1 and March 2, according to the weekly flu report released Friday by the US Centers for Disease Control and Prevention.
"We're still having flu. And we're still seeing a steady stream of patients who are being admitted to hospital with influenza," said Dr. William Schaffner, medical director of the National Foundation for Infectious Diseases.
Nine additional children died of flu-related causes during the week ending March 2, bringing the total to 64 for the season. However, not all flu-related deaths are detected or reported, so the CDC believes the actual number of deaths to be higher.
For adults, flu deaths are estimated based on pneumonia and other illnesses related to flu. The proportion of deaths attributed to pneumonia and flu during the week ending February 23 was 7.5%, slightly higher than the usual threshold of 7.3% for this time of year, the CDC said, based on data from the National Center for Health Statistics.
It's unclear whether the season has peaked, but there are still weeks of flu activity to come this season, with 48 states and Puerto Rico reporting widespread activity.
The CDC also recorded about 37 hospitalizations per every 100,000 people during the week ending March 2. This is the overall rate, with a higher proportion of people who are 65 and older requiring hospitalization (107 per every 100,000), followed by children up to age 4 (49 per every 100,000) and then people between the ages of 50 and 64 (48 per 100,000).
Hospitalization rates are a lot lower than last season, the CDC said.
The H1N1 virus strain has dominated this season, but H3 viruses have been circulating in the Southeast, according to Schaffner. It's been a "double-barreled influenza outbreak this year," he said, with H1N1 seen throughout most of the country and two waves of H3N2 infections in the southeastern United States. H3N2 viruses account for about two-thirds of influenza A viruses tested this past week, according to the CDC.
"H3N2, in general, produces more severe disease," he said. "That was the virus that was causing so much trouble last year."
"All of these viruses, but particularly H3N2, have a tendency to try to put you in the hospital and set you up for a secondary case of pneumonia."
Everyone 6 months or older should get vaccinated against the flu, the CDC advises. People over 65, children under 2 and individuals with medical conditions should also get a pneumococcal vaccination to prevent pneumonia.
"If you become sick, please call your health care provider, because they may well provide a prescription for antiviral drugs that can help reduce the severity and duration of your illness," Schaffner said. Common antivirals include Tamiflu and Xofluza.
Although the CDC continues to recommend getting a flu shot, Schaffner noted that it is "awfully late" in the season, because it takes 10 days to two weeks after getting the shot for your body to develop immunity. Still, as long as flu is circulating in the area where you live, it is not too late to get vaccinated. He also advises his patients to "remember to get it this fall in preparation for the next flu season."
"Although it's not perfect, it still prevents many, many infections, and even if you should get influenza despite having received the vaccine, it tends to make a less severe infection. You are certainly less likely to get the complications of pneumonia, having to be hospitalized and dying," Schaffner said.