When autumn faded in the winter of last year, some infectious disease researchers began to divert attention from the Covid-19 pandemic and return to something more familiar. This was the time of year when they usually began to examine the number of flu, the seasonal flu, to see how far the outbreak would be and to assess the extent to which that year’s vaccine treated the respiratory protean virus.
The answer was: bupkis. Hardly anyone was sick or dying of the flu. A year earlier, during the 2019-2020 flu season (basically fall and winter, with highs in December, January and February), 18 million people in the U.S. saw a doctor for their symptoms and 400,000 had to be hospitalized. In all, 32,000 people died. But in the current season, the cases barely exceeded four digits. “There is always a vaccine season and a flu season. We’re used to working on that pattern, and the pattern is gone, ”says Emily Martin, an epidemiologist at the University of Michigan School of Public Health who is part of the Influenza Control and Prevention Centers’ network Diseases. “Now, I’m glad I didn’t have to do Covid control and flu control at the same time. That would have been a disaster. But at the same time, it’s a strange year. “
It’s weird. And it’s not just the flu. Case figures for respiratory syncytial virus, which mainly affects babies and, like the flu, have a seasonal rhythm. According to a document released last week, the list of missing people also includes enterovirus D68, a likely culprit for acute flaccid myelitis from childhood disease, similar to polio. The virus and AFM come and go in an approximate cycle every two years, and the last round in North America was in 2018. In 2020, they also lost track.
He Because it’s not really a mystery. Probably. Most likely, the entire mask, physical distancing, hand washing, and other “non-pharmaceutical interventions” that everyone agrees on will be put on almost everyone, who did to prevent the spread of Covid-19, also put the kibosh on those other viruses. This is not the only hypothesis there is, but it is good.
The mystery is the how and what-next. The answers can teach scientists more about how these other diseases infect people and how to stop them. It is unclear why these NPIs crushed at least three other respiratory viruses as Covid-19 spread. And even less clear is what a flu-free year would mean for next winter and for subsequent winters. According to an estimate, the flu kills between 12,000 and 61,000 people in the U.S. each year and costs the economy $ 11 billion annually. For decades, even centuries, people have just accepted this risk. But if it turns out that it can be avoided almost completely, will the willingness to tolerate risk also change?
Pandemics occur when a virus reaches its evolutionary channel. The virus that causes Covid-19 is called SARS-CoV-2, and when it fell in late 2019, no human immune system had ever seen it. No one had any defense. The fact that people who had no symptoms could transmit it made it different from most of its respiratory pathogenic cousins, different enough to take advantage of human social interactions and globalize.
But, just as it only takes the smallest circumstance or a genetic twist to turn a virus into a pandemic, the version of the disease on a sand-filled band is also not necessary to limit a disease to ‘equivalent to playing small clubs. “Covid-19 control measures (mask wear and social distancing) really work and work very well for other respiratory pathogens,” says Rachel Baker, an epidemiologist at Princeton University. The key difference is probably that these other diseases have been wearing concerts for thousands of years and that humans are a little delighted with their charms. Even the flu, with its famous mutable genome that requires a new vaccine every year, leaves behind a certain level of immunity on a population scale. “With seasonal diseases, we have a lot of population immunity, we have vaccines and most people over the age of 2 have had RSV,” Baker says. “That’s why we don’t have a seasonal pandemic.”