Experts predict ‘severe’ flu season once COVID-19 restrictions relaxed

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While the world may be anxious to get back to pre-pandemic living, a new study warns that as soon as COVID-19 precautions end, the flu will make a big comeback.

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Researchers from Columbia University in the US published a report which suggested that COVID-19 preventative safety measures – such as face masks and social distancing in public spaces - have been helping protect the public from the flu, meaning that the world’s overall flu immunity has waned since the rules were implemented.

Throughout the first ten weeks of COVID-19 safety measures, influenza infection rates decreased by 60 percent. Researchers believe that once those rules are lifted, far more people will get infected than ever before.

“In the short term, measures to control the spread of the coronavirus will likely continue to suppress the number of influenza infections, but after these measures are relaced, with greater population-wide immune susceptibility to influenza could lead to a large outbreak,” study author Sen Pei, PhD, assistant professor of environmental health sciences, was quoted as saying in a university release.

“This year, it’s more important than ever to get your flu shot. While we’re rightly focused on protecting ourselves against COVID-19, we shouldn’t forget about the flu, which can be fatal,” Pei added.

The scientists used a computer model of influenza A/H1 and B, which circulated in early 2020, to quantify the reduction of incidence and transmission after the implementation of non-pharmaceutical interventions (NPI) – which include travel restrictions, face masks, social distancing, school closures and other prevention measures - in most US states on March 15, 2020.

The scientists also projected influenza transmission at the national scale across the US over the next five years. The model used data from the country’s Centers for Disease Control and Prevention (CDC) FluView website.

Large outbreak predicted followed by years of severe flu seasons

According to their projections, a large-scale influenza outbreak will likely take place as soon as public health measures are relaxed.

Scientist in a lab. (Unsplash, CDC)
Scientist in a lab. (Unsplash, CDC)

In following seasons, outbreaks are also expected to be elevated, gradually returning to pre-pandemic levels, according to the research.

Over the last ten years, US influenza deaths ranged between 12,000 in 2011-12 to 61,000 in 2017-18.

“Our projections show that the downstream, ripple-effects of pandemic public health measures could persist for a number of years,” said Pei.

Severity of next flu outbreak

Researchers explained that the next flu outbreak could be bad.

“The longer the control measures are in place before they are lifted, the greater the number of individuals who will be susceptible to an influenza infection – a situation that could lead to a more severe outbreak in parts of the country that had high levels of adherence to masking and other public health measures during the pandemic,” the university release stated, citing the study.

The scientists also anticipate that the global suppression of influenza activity during the pandemic could make it difficult to predict future strains, hence having a potentially adverse impact on the production of effective influenza vaccines.

A nurse prepares an injection of the influenza vaccine at Massachusetts General Hospital in Boston, Massachusetts. (File photo: Reuters)
A nurse prepares an injection of the influenza vaccine at Massachusetts General Hospital in Boston, Massachusetts. (File photo: Reuters)

“… suppression of influenza during the pandemic could lead to a surge of multiple influenza strains, including the A/H3 strain which has a high mortality rate and hasn’t been widely circulating since the 2018-2019 season. All these factors would contribute to a more severe outbreak,” according to the statement issued by the university.


Like many studies, it has its limitations as well.

The statement said that the suppression of the flu during the ten-week study period could be “overstated” in the data due to peoples’ reluctance to seek medical help for non-emergencies throughout the COVID-19 pandemic.

“Another question is whether or not antigenic escape (viral mutations that allow it to evade the immune system) rather than waning immunity is the predominant mechanism in the accumulation of population susceptibility to influenza.

If so, influenza would have less opportunity to mutate while public health measures are in place. A more durable influenza immunity would also result in fewer people being susceptible to influenza when public health measures are lifted. All these possibilities would contribute to a less severe outbreak,” the statement read.

Read more:

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COVID-19 reinfection likely for unvaccinated: Study

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