Social distance has almost extinguished the spread of influenza and other respiratory viruses. But that means that future outbreaks can be serious – and can occur at odd or unexpected times, experts warn.
In the short term, fewer cases of the flu means less flu deaths and hospitalizations, alleviating health systems a little already hit with COVID-19, The Atlantic reported. Cases of other seasonal viruses, including respiratory syncytial virus (RSV), common cold coronavirus and parainfluenza viruses, which cause infections of the upper and lower respiratory tract, have also declined to remarkably low levels this year, probably due to coronavirus-related precautions, such as masking, physical distance, hand washing and limited international travel.
But experts predict that this seasonal virus truce could leave us vulnerable, as fewer people will be exposed and gain immunity to circulating strains.
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“Susceptibility is increasing in the population,” Shweta Bansal, a disease ecologist at Georgetown University in Washington, DC, told the atlantic.
For example, children with no previous exposure to the viruses will be born, as usual, but will find fewer viruses than in a normal year; however, the immunity in previously exposed adults it will begin to decrease. People without immunity or with reduced immunity “are like fuel for the flu fire,” said Bansal. “The more fuel that is available, the easier it will be for an outbreak to happen.”
The match can be closed when the precautions of COVID-19 disappear, triggering a recovery from infections, Rachel Baker, an epidemiologist at Princeton University, Science News said. As the size of the susceptible population increases, “we need to be prepared for out-of-season outbreaks and potentially large outbreaks,” said Baker.
For example, New South Wales, Australia, generally has peak RSV cases between April and June, but during the 2020 season, the number of positive RSV tests fell by more than 85% compared to the past few years, reported the Science News. But in late December, after COVID-19 restrictions in New South Wales were lifted, RSV cases skyrocketed; typically, only a few hundred cases are reported in late December, but by 2020, 6,000 positive RSV tests emerged in just two weeks.
This Australian case “may be an interesting harbinger of what’s to come in the northern hemisphere,” Baker told Science News.
Scientists still don’t know whether the next flu seasons will be bad, The Atlantic reported. But the lack of circulating flu strains makes it more difficult to prepare for the season. Scientists would normally track how different strains of influenza mutation over time, in order to predict which versions of the virus may prevail in the coming season. This initial sample helps them to formulate a new flu vaccines in advance.
But with so few flu cases to sample this year, scientists are running low on data. The low level of circulation could theoretically extinguish certain strains of flu, Florian Krammer, virologist and flu specialist at the Icahn School of Medicine on Mount Sinai, told The Atlantic. But, on the other hand, new strains can emerge without scientists knowing about them, he said.
You can read more about future flu seasons at Science News and The Atlantic.
Originally published on Live Science