Health officials are predicting this winter could see an active flu season on top of possible COVID flare-ups. In short, it’s a good year to be a respiratory virus. Left: Image of SARS-CoV-2 omicron virus particles (pink) replicating inside an infected cell (teal). Right: Image of an inactive H3N2 influenza virus. Hide NIAID/Science Source subtitles
The flu practically disappeared for two years as the pandemic raged. But influenza seems poised to make a comeback in the US this year, threatening to trigger a long-feared “twindemic.”
While the flu and coronavirus are both notoriously unpredictable, there’s a good chance COVID cases will surge again this winter, and worrying signs the flu could return as well.
“This could very well be the year that we see a twin demia,” says Dr. William Schaffner, Professor of Infectious Diseases at Vanderbilt University. “That means we have a spike in COVID and a spike in influenza at the same time. We could both affect our population at the same time.”
The strongest indication that the flu could hit the US this winter is what happened during the Southern Hemisphere winter. The flu returned to some countries such as Australia, where respiratory infection started to rise months earlier than normal, causing one of the worst flu seasons in recent years.
What happens in winter in the southern hemisphere often gives a foreshadowing of what will happen north of the equator.
“If we have a serious flu season, and if the Omicron variants continue to cause mostly mild diseases, next winter could be a much worse flu season than COVID,” Schaffner warns.
And the combination of the two viruses could put a serious strain on the healthcare system, he says. The Centers for Disease Control and Prevention estimates that the flu causes between 140,000 and 710,000 hospitalizations annually.
“We should be concerned,” says Dr. Richard Webby, an infectious disease specialist at St. Jude Children’s Research Hospital. “I don’t necessarily think it’s a fear. But we have to worry.”
The main reason the flu has basically disappeared over the past two years has been the behavioral changes people have made to avoid COVID, such as: E.g. staying at home, avoiding public gatherings, wearing masks and not traveling. This also prevented the spread of influenza viruses. However, these measures have largely been abandoned.
“As community containment measures begin to roll in around the world and people return to their normal activities, the flu has started to spread around the world,” says Dr. Alicia Fry, who leads influenza epidemiology and prevention for the CDC. “We can expect a flu season this year – for sure.”
Young children are particularly at risk
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The CDC reports that the flu is already beginning to spread in parts of the South like Texas. And experts are warning that very young children could be particularly at risk this year.
Although COVID-19 has generally been mild for young people, the flu typically poses the greatest threat to both the elderly and children. The main flu virus currently circulating, H3N2, hits the elderly particularly hard. But health experts are also worried about young children who haven’t been exposed to the flu in two years.
“You have the 1-year-olds, the 2-year-olds and the 3-year-olds, all of whom are going to see it for the first time, and none of them have any pre-existing immunity to influenza,” says Dr. Helen Chu, Assistant Professor of Medicine and Allergy and Infectious Diseases and Associate Associate Professor of Epidemiology at the University of Washington.
In fact, the flu seems to have hit younger people in Australia particularly hard.
“We know that schools are really where influenza spreads. They really are seen as drivers of transmission,” says Chu. “They will be the spreaders. They will then take it home to the parents. The parents then take it to work. They take it to the grandparents who are in assisted living or nursing home. And then those populations get really sick with the flu.”
“I think we’re headed for a bad flu season,” says Chu.
“Viral interference” could offset the risks
Some experts doubt that COVID and flu will hit the country at the same time due to a phenomenon known as “viral interference,” which occurs when contracting one virus reduces the risk of contracting another. That’s another possible reason why the flu has disappeared in the last two years.
“These two viruses can still both occur in the same season, but my gut feeling is that they will occur sequentially and not both at the same time,” says Webby. “That’s why I’m less worried about the Twindemic.”
Still, Webby and others are urging people to make sure all family members get a flu shot as soon as possible, especially when flu season starts early, even in the US. (Most years, officials don’t urge people to get the flu shot until October.)
So far, it looks like this year’s flu vaccines are a good match for circulating strains and should therefore provide effective protection.
But health officials fear fewer people than usual will be vaccinated for the flu this year as anti-vaccination sentiment has increased in response to COVID vaccinations. Flu vaccination rates are already lagging behind.
“We are concerned that people are not being vaccinated. And the influenza vaccine is the best prevention tool we have,” says Fry of the CDC.
Fry also hopes some of the habits people have developed to fight COVID will continue and help mitigate the effects of the flu.
“The joker here is that we don’t know how many mitigation practices people are going to adopt,” says Fry. “For example, people are now staying at home when they are sick instead of going to work. They keep their children out of school. The schools strictly do not let children come to school when they are sick. All of these things could reduce transmission.”