What happened to coronavirus, flu 'twin-demic'? Experts weigh in

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Flu hospitalizations drop this year amid coronavirus pandemic

Dr. Marc Siegel tells ‘Fox & Friends Weekend’ that public health measures such as mask-wearing have contributed to the decline.

With coronavirus cases soaring in late summer, experts warned about the potential for a so-called "twin-demic," which they said would've seen hospital systems overwhelmed by both COVID-19 and the influx of flu patients, but the surge never came. In fact, the Centers for Disease Control and Prevention (CDC), is reporting that flu activity in the U.S. "remains lower than usual for this time of year," which is typically the peak of illnesses.

Since Oct. 1, 2020, or the start of flu season, there have been 165-laboratory confirmed flu-related hospitalizations in the U.S. According to the CDC, not only is this below average for this point in the season, it’s the lowest rate seen since data collection began in 2005.

So why did the influenza virus take a backseat to coronavirus? Experts say it’s a mix of factors, but mitigation measures put in place to stop the spread of COVID-19 likely played a big part.

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"The same phenomenon was found in the Southern Hemisphere during the winter there (the opposite months from ours) last year and was thought to be caused by the ‘non-pharmaceutical interventions’ adopted to prevent the spread of COVID-19 – masks, sheltering and social distancing, frequent handwashing, and avoiding indoor crowds," Dr. Henry Miller, former FDA official and currently a senior fellow in health studies at the Pacific Research Institute, told Fox News.

School closures also likely played a role, as early research suggests kids transmit the influenza virus better than they do COVID-19, Dr. Abisola Olulade, a family medicine physician in California, explained.

Coronavirus mitigation measures like social distancing and wearing a mask also likely contributed to low spread of flu virus, experts say (iStock)

"Transmission of flu is harder than the transmission of coronavirus," Olulade told Fox News. "Mitigation measures were more limited in their ability to prevent people from getting COVID."

Olulade said the impact mitigation measures had on the decrease in flu cases raises an interesting question of whether some, such as the use of face masks while in public, may remain in place once the pandemic ends.

"I can’t imagine that the CDC isn’t thinking about this and I hope they are because it’s made such a huge difference," she said.

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Olulade also pointed out that while some may suggest that people weren’t testing for the flu amid coronavirus, the positivity rate of those who were remained lower than usual, which indicates that the viral spread in the community was indeed low, and not a matter of what test was conducted.

Dr. Eric Legome, chair of emergency medicine at Mount Sinai West and Mount Sinai Morningside, noted that there wasn’t just a decrease in flu activity this year, but in other common respiratory illnesses as well. Legome said that a longer incubation period, greater infectiousness, and no previous levels of immunity to coronavirus also likely contributed to the surge in cases while other illnesses saw low activity.

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"It is hard to predict what will happen with influenza and other seasonal viruses next year (or any one year, and next year is particularly difficult)," Legome told Fox News. "The current interventions such as masking, etc., may be necessary for a prolonged time. This may serve to prolong the reduction in respiratory disease. It has been theorized, however, once these measures are reduced or eliminated, there may be a significant increase over historical numbers of these infections. That is, we may see unusually severe cold and flu seasons due to factors such as increase susceptibility to some of these diseases."

Miller said that the strength of the flu virus next year will come down to a matter of probabilities and that it’s impossible to predict whether a dangerous mutant – one that drives new infections – will appear. The vaccine developed for next year may also play a role in how the season goes, but it could be difficult to come up with the right formula based on the low number of strains that circulated this season. 

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"We determine the vaccine strain by what happens in the Southern Hemisphere," Olulade continued. "If we don’t have enough information, are we going to select the right strain in the vaccine? We also don’t want to cause hesitation about the vaccine – even if it’s not completely protective it does decrease [the] strength of the virus."