As autumn faded until the winter of last year, a couple of researchers with infectious diseases began to turn their attention away from the Covid-19 pandemic and back to something more well-known. This was the time of year when they usually started looking at their numbers for the flu, the seasonal flu – to see how bad the outbreak would be, and to assess how well that year’s vaccine handled the protean respiratory virus.
The answer was: bupkis. Hardly anyone was sick or died of the flu. A year earlier, in the 2019-2020 flu season – basically autumn and winter, which peaked in December, January and February – 18 million people in the United States saw a doctor for their symptoms, and 400,000 had to be hospitalized. In all, 32,000 people died. But in the current season, cases barely crossed four digits. “There is always vaccine season and flu season. We are used to working in 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 Center for Disease Control and Prevention’s influenza surveillance network. “Now I’m glad I did not 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 this strange year. ”
Strange. And it’s not just the flu. Case numbers for respiratory syncytial virus, which primarily affect babies and for which influenza has a seasonal rhythm, also bound. According to one paper which came out last week, the list of missing actions also includes enterovirus D68, a likely culprit behind the polio-like children’s disease, acute slap myelitis. The virus and AFM come and go on an approximately every two years cycle, and the last round in North America was in 2018. In 2020, they also missed their signal.
That Why of it is not really a mystery. Probably. Most likely, everything wearing the mask, physical distance, washbasin and other “non-pharmaceutical interventions”, all of which – OK, almost all – did to prevent the spread of Covid-19 also add kibosh on the other viruses. That is not the only hypothesis, but it is good.
The mystery is how and what-the-next. The answers can teach researchers more about how these other diseases infect humans and how to stop them. The mechanics of why these NPIs shattered at least three other respiratory viruses while Covid-19 ran violently are not clear. And even less clear is what a year without the flu will mean for next winter and for winters after that. Influenza kills 12,000 to 61,000 people in the United States each year and costs the economy $ 11 billion annually, according to a discretion. For decades, even centuries, people have just accepted this risk. But if it turns out that it can be almost completely prevented, will people’s willingness to tolerate the risk also change?
Pandemics happen when a virus hits its evolutionary groove. The virus that causes Covid-19 is called SARS-CoV-2, and when it dropped in late 2019, no human immune system had ever seen it before. No one had any defense. The fact that people who had no symptoms could transmit it did so differently than most of its respiratory pathogen cousins - just different enough to take advantage of human social interactions and become global.
But just as it takes only the slightest circumstance or genetic twist to turn a virus into a pandemic, the disease version of an arena-filled band, it also does not take much to limit a disease to the equivalent of playing small clubs. “The Covid-19 controls – mask wearing and social distancing – really work, and they also work really well for other respiratory pathogens,” says Rachel Baker, an epidemiologist at Princeton University. The main difference is probably that the other diseases have played concerts for thousands of years and people are a little assured of their charm. Even influenza with its famous mutable genome, which requires a new vaccine every year, leaves a certain level of population-scale immunity. “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 you do not have a seasonal pandemic.”