As last winter was about to begin, some infectious disease researchers took their eyes off COVID-19 for a while back to follow up on an epidemic more familiar to them: seasonal flu. At this point of the year, the United States begins to see a dizzying increase in the number of flu cases.
During the three months of winter, the peak of the flu epidemic in 1029-2020, about 18 million people in the United States had to see a doctor because of fever, headache, and stuffy nose. Of those, at least 400,000 people were hospitalized and 32,000 died.
This makes some health experts in the US worried that this year’s flu season, they will have to deal with 2 pandemics at the same time. But until now, when the peak of February has passed, the whole United States has only recorded no more than 10,000 cases of flu infection, an unprecedented decline. Basically, the flu seems to have disappeared, almost no patients died.
Emily Martin, an epidemiologist from the University of Michigan School of Public Health working for the US CDC influenza surveillance network, said: “At this point I can be glad I didn’t have to deal with both COVID and flu at the same time. If that happens it would be catastrophic. This year’s flu season is so weird.”
The strange thing that happened not only for the flu. The number of general respiratory viral infections, including those affecting mainly infants, has also fallen to its lowest level in many years.
The reason for this trend is still a mystery. But perhaps, and most likely, it is our practice of COVID-19 preventive measures such as wearing a mask, keeping distance and washing hands. These preventive measures have been shown to be effective against other respiratory viruses as well.
According to an earlier estimate, seasonal flu could kill between 12,000 and 16,000 Americans a year and cause $ 11 billion in damage to the economy, including lost labor costs. For decades, even centuries, Americans accepted that.
Will the United States give up a bit of personal freedom to prevent future flu seasons after the lessons of COVID-19 preventive measures such as wearing a mask, washing hands and keeping social distance? ?
If the answer is “is not“Epidemiologists warn America is likely to suffer a”Punishment” when the influenza virus returns after the COVID-19 pandemic, it may be in the winter of next year. This is because the absence of this year’s flu season also means that immunity in the population to the flu virus has not been established.
When the flu virus returns for the next season, every year, it will accumulate a larger number of mutations, the vaccine will most likely not be effective against that strain anymore. Therefore, after all, the disappearance of this year’s seasonal flu in the US is not necessarily good news for them.
Using the SIR epidemiological model to track the number of people susceptible to influenza, the number of people infected and recovering, the US scientists warn: After a flu season, none of the sensitive people turned into humans. infected, the next flu season will be a much worse flu season.
“We know that with the flu, your body’s antibody protection weakens over time. This year our entire population has not developed resistance.Martin explained. “That means next year’s flu strains will have a more open playing field. ”
The SIR pattern shows similar ups and downs of other respiratory viral strains such as enterovirus D68 that often infect infants. The increase or decrease every 2 years of this strain usually coincides with the increase or decrease of the susceptible population.
“When you have a large outbreak, a lot of people in the community are infected. Then things slack, you need more time to accumulate a sensitive population that reaches a certain threshold. Then you have another outbreak“, Said Sang Woo Park, a graduate student in ecology and evolutionary biology at Princeton University.
That is how flu patterns work year by year. But this year, with the absence of flu, Park said the population’s susceptibility is on the rise and next year’s flu season could be a flu season where outbreaks are very strong.
If all of that is true… well, would you like to hear the good news first or the bad news?
The good news is that the babies won’t get the respiratory viruses like the cells from RSV until they get older, and usually they will only get mild illness. “Maybe that’s better for the kids“Martin said. “But we’re not really sure.”
The bad news is, if the flu virus had an extra year to accumulate mutations, they might be resistant to the vaccine America had to deal with it from last flu season.
Usually the flu will run from one hemisphere to another, from winter to winter, just like a skier looking for places where they can satisfy a passion of continuity.
And vaccine makers can track what has happened in one hemisphere in preparation for the other hemisphere flu season. But that was not true this year. Martin said: “This rhythm has been interrupted this year. Now we don’t have enough data to fully understand what’s going to happen here. “
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