"We've noted that flu activity is starting to increase across much of the country," Rochelle Walensky, director of the US Centers for Disease Control (CDC), told NBC News on Friday.
"Not everybody got flu vaccinated last year, and many people did not get the flu. So that makes us ripe to have potentially a severe flu season,” she added.
The “season” for influenza, when the majority of outbreaks happen each year, typically begins in December and peaks in February, the coldest months in the United States.
Between 12,000 and 52,000 Americans die from influenza in a typical year in the United States, according to CDC data, although years with particularly bad outbreaks can be much higher. During the winter of 2017-2018, for example, 80,000 died in the US from the viral respiratory illness.
According to the CDC’s most recent weekly report, released on Friday, the vast majority of cases are Influenza Type A (H3N2), and are concentrated in New York City, Washington, DC, Georgia, and Texas. Type A Influenza includes several strains associated with highly deadly outbreaks, including pandemics in 1918 and the late 2000s.
Health officials have said they are expecting the coming winter to be worse than several recent years because most masking restrictions have been lifted across the US. Masking had a noticeable effect on limiting the spread of influenza and other respiratory illnesses in addition to COVID-19 - so much so that one lineage, the B/Yamagata strain, is believed to have gone extinct as a result.
Christine Paik, a spokesperson for the Poway Unified School District in San Diego, California, told CNN on Wednesday that nearly 400 students were absent in a single day “with cold and flu-like symptoms.”
“Health officials have told us that the cold/flu season is definitely here and it’s hitting schools harder now that COVID restrictions are no longer in place,” she said.
The CDC is recommending that as many people as possible get their flu shots, which is an annual vaccination against what officials have judged to be the most likely influenza strains to cause a serious outbreak that year.
“An annual flu vaccine is the best way to protect against flu. Vaccination helps prevent infection and can also prevent serious outcomes in people who get vaccinated but still get sick with flu,” according to the report.
“CDC recommends that everyone ages 6 months and older get a flu vaccine, ideally by the end of October,” it continues. “There are also prescription flu antiviral drugs that can be used to treat flu illness; those need to be started as early as possible.”