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Flu activity has been minimal this winter. Noam Galai/Getty Images
  • Flu season has been mild this year, thanks to the mitigation measures used to contain COVID-19, such as physical distancing and mask wearing.
  • School and office closures also contributed to the unusually inactive flu season.
  • The mitigation measures curbed influenza activity even though COVID-19 surged.

Last summer, infectious disease specialists warned that the COVID-19 pandemic could spiral into a “twindemic” when seasonal influenza hit.

But that nightmare scenario never unfolded. The flu didn’t get a strong footing in the United States this season and a twindemic never struck.

COVID-19 is likely far more contagious than the flu.

Because the virus that causes seasonal influenza spreads via respiratory droplets, the safety precautions used to prevent COVID-19, such as mask wearing and physical distancing, also helped cut down flu activity.

Due to influenza’s short incubation period and widespread population immunity, the measures used to stop the spread of COVID-19 also caused flu activity to drastically drop.

Between Oct. 1 and Jan. 30, only 155 people in the United States have been hospitalized with the flu.

That’s a 98 percent decrease from the same window of time in the 2019-2020 flu season in which 8,633 people were hospitalized with the flu.

The precautions used to prevent COVID-19 ended up drastically reducing influenza transmission.

Both are respiratory infections that spread via aerosol droplets.

“Any precaution you take to avoid COVID will also reduce your risk of contracting an influenza virus. Hand washing, social distancing, and wearing masks are certainly driving down cases of the flu,” said Dr. Casey Kelley, a family medicine physician and the founder and medical director of Case Integrative Health in Chicago.

The closure of schools also contributed to this year’s low flu activity.

According to Kelley, children have less immunity to the flu since their immune systems haven’t been exposed to many pathogens.

Schools are also high-contact environments, making kids particularly susceptible to catching and transmitting the flu.

Past evidence suggests kids are the number one source responsible for bringing the flu into households.

Like schools, offices are flu hotspots.

Flu germs can live on common surfaces — like doorknobs or the copy machine — for up to 24 hours. They also shoot through the air when a person coughs, sneezes, or exhales.

“Public transit, office buildings and business travel are all high-contact events that are down significantly [this year],” Kelley said.

COVID-19 is thought to be far more infectious than the flu especially as few people have immunity against this new disease.

Researchers calculate the contagiousness of a disease by looking at the R number, which represents how many people, on average, a person with the disease will spread the virus to.

The R number for COVID-19 is thought to be around 2 to 3, whereas the R number for influenza is around 1 or 2.

“No one on Earth had antibodies to COVID-19 when the outbreak started, so every interaction was an opportunity for it to spread,” said Kelley, adding that we’ve had years to build up at least partial immunity to influenza.

COVID-19 also has a longer incubation period that can last up to a couple of weeks. With the flu, people typically develop symptoms just a couple of days after being exposed to the virus.

“Most people with the flu experience symptoms relatively early in their illness — usually within 2 days of exposure,” said Dr. John Showalter, an expert in communicable diseases and the chief product officer of Jvion in Suwanee, Georgia.

Once flu symptoms begin, people usually isolate themselves, reducing the chance they’ll transmit the virus.

“With COVID-19, individuals can actively spread the virus for up to 7 days before they experience symptoms,” Showalter said.

In addition, COVID-19 often causes irregular symptoms, such as gut issues or headache.

“This means many don’t even realize they have — or are spreading — the illness for a week or longer, and likely have not altered their interactions with others during that time,” Showalter said.

When the pandemic restrictions are lifted, experts suspect the flu will make a comeback.

“Flu is one of the most consistent and persistent illnesses in recorded medical history, with reports of influenza-like illness dating back to ancient Greece,” Showalter said.

While we will likely see minimal flu activity in the 2021-2022 flu season due to continued safety precautions, Showalter said the flu “isn’t going anywhere.”

Kelley is hopeful that the mitigation measures adopted to contain COVID-19 will last and help contain the flu in the future.

“Building and maintaining a strong immune system, washing hands, self-isolating when you don’t feel well, and even wearing a mask during the peak flu season will all reduce the spread of flu, even after the pandemic is history,” Kelley said.

The flu season has been historically mild this year, thanks to the mitigation measures, such as physical distancing and mask wearing, used to contain the spread of COVID-19.

School and office closures also contributed to the unusually inactive flu season.

The mitigation measures used to control the spread of COVID-19, along with the widespread population immunity against the flu, helped curb influenza activity this year.

However, while flu activity has been unusually low this season, COVID-19 has surged.