While flu activity last year was abnormally low—likely because of Covid-19 precautions—flu activity this season is starting to rise, raising fears that the U.S. could face a "normal flu season" on top of a severe Covid-19 surge.

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Flu activity starts to rise

According to CDC data, a total of 634 new flu cases were reported for the week ending in Dec. 25, down from 1,040 for the previous week. During the same time period in 2020, the United States saw just 114 and 101 new flu cases in those weeks, respectively.

Reports of influenza-like illnesses are rising among all age groups, but especially among those ages 0 to 4 years old, CDC data shows. For the week ending in Dec. 25, 10.9% of outpatient visits for respiratory illnesses among 0 to 4-year-olds were for influenza-like illnesses, up from 9.9% the week prior.

According to CDC, the states showing "high" or "very high" activity of influenza-like illnesses include:

• Alabama
• Alaska
• Florida
• Georgia
• Iowa
• Massachusetts
• Missouri
• Nevada
• New Jersey
• New Mexico
• New York
• North Dakota
• Ohio
• Oklahoma
• South Carolina
• Tennessee
• Virginia

Hospitalizations for influenza are also on the rise. According to CDC data, 1,825 new hospital admissions for influenza occurred the week ending in Dec. 25, up from 1,269 the week before.

So far this flu season, two children have died of influenza, according to CDC. During last year's flu season, just one child died, compared to 199 in the 2019-20 flu season and 144 in the 2018-19 flu season.

2021-22 flu season seems to be 'more of a normal flu season'

During the 2020-21 flu season, some major cities in the United States saw zero influenza cases, and overall, case numbers were abnormally low. Experts said measures meant to stem the spread of Covid-19, including school closures, social distancing, mask-wearing, and canceled travel, likely contributed to lower flu numbers.

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However, according to Lynnette Brammer, who tracks influenza-like illnesses for CDC, "This is setting itself up to be more of a normal flu season."

The pediatric deaths are "unfortunately what we would expect when flu activity picks up," Brammer said. "It's a sad reminder of how severe flu can be."

According to Brammer, the type of influenza virus circulating this year is one that tends to cause the largest amount of severe disease, especially among the young and elderly.

Last year's low-activity flu season made it difficult to plan this year's flu vaccine, the Associated Press reports. According to Brammer, the virus that is circulating so far seems to be from a slightly different subgroup than what is targeted by the vaccine. Brammer added, however, that it's "really too early to know" whether that will affect the vaccine's effectiveness.

"We'll have to see what the impact of these little changes" will be, Brammer said. "Flu vaccine is your best way to protect yourself against flu." (Tebor et al., USA Today, 12/28/21; Johnson, Associated Press, 12/27/21)