Colds Nearly Vanished Under Lockdown. Now They’re Coming Back

The return of colds has been less pronounced so far in the United States, where schools are less likely to have reopened. But there is evidence that infections are rising. Data from the Seattle Flu Study, which tracks a wide range of respiratory illnesses, indicates rhinoviruses were on the upswing beginning in early August, after nearly vanishing in late spring. The early consensus: It’s time to prepare. “This is paramount for all of us,” says Steven Pergam, a professor of infectious disease at the Fred Hutchinson Cancer Center in Seattle. “Testing labs have been so focused on Covid that we’re trying to shift the focus to identifying when other respiratory viruses are in our communities. It’s going to put on a lot more pressure.”

“Covid presents a challenging dilemma because of the range of symptoms,” says Kelly Wroblewski, director of infectious disease at the Association of Public Health Laboratories. “When you see sniffles in a kid, you’re more likely to want to seek a Covid-19 test.” That confusion could put more strain on a precarious supply chain of swabs, reagents, and testing machines. One focus now, Wroblewski says, is to develop panel tests that can distinguish between various respiratory pathogens that can cause more severe disease, including Covid-19, influenza, and respiratory syncytial virus (RSV), a cold-causing virus that typically follows in the wake of rhinovirus season and can lead to more severe disease in very young and old people.

One reason why rhinoviruses leapt back into action at soon as conditions were right is their sheer ubiquity, says Ian Mackay, an associate professor at the University of Queensland in Brisbane, Australia, who spent years studying “rhinos,” as he calls them. Dozens of rhinoviruses may circulate at one time in a community. “They’re always kicking around, because there are so many of them,” he says. And because the viruses have co-evolved with humans over time, they’re well suited to jumping from person to person and living within us, undetected, during lockdown.

That hermetic quality is distinct from certain strains of influenza, which globe-trot along with international travelers. (Closed borders, plus the timing of stringent lockdowns, are thought to be factors that kept the southern hemisphere’s flu season at bay.) Rhinoviruses were ready to come back as soon as school did. “Rhinos love childcare,” Mackay says. That’s in part because children’s immune systems haven’t yet seen many of those rhinovirus varieties, so kids get sick—or at least the sniffles—again and again and again, and they pass the germs along to others.

A question, however, is why the cold viruses appear to be spreading so quickly abroad now in spite of continued mask-wearing and social distancing. Europeans and Australians may be enjoying more of the finer things in life than Americans, but they’re still battling the same pandemic. The differing structures of the virus may play a role. The virus that causes Covid-19 is what’s called an “enveloped” virus, a ball of protein surrounded by a lipid layer. That fatty external structure is easier to destroy with soap and water, and it’s less likely to remain infectious for long on exposed surfaces. That’s one reason health officials now place more emphasis on masks and distancing to help prevent aerosol and droplet spread of SARS-CoV-2, and less on disinfecting grocery bags and doorknobs. Rhinoviruses, however, don’t have that envelope, and are thought to be hardier. “Kids will drag their hands through everything and be festy little carriers of the virus,” Mackay says.

Sebastian Johnston, a leading expert on rhinoviruses at Imperial College London, says that while that’s likely the case, he believes aerosols and droplets are probably still the main route for rhinoviruses to get around—same as SARS-CoV-2. That means masks and distancing help curb those viruses too. But the difficulty of getting kids to uniformly abide by those rules, plus children’s susceptibility to passing colds to each other, plus the viability of surfaces as an alternative route of transmission, are all likely coming together to fuel the current outbreaks. Kids are getting these viruses, somehow—just like any other school year—and then bringing them home with them.

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This year, that’s coming at a bad time in places like the UK. The return of cold season has coincided with a surge in Covid-19 cases, and just as people are being required to stay home from work and schools if they have any symptoms of illness. Hence the run on emergency room tests from worried parents, despite government officials urging tests to be used sparingly. “The testing system is overwhelmed by demand, and a lot of that demand will be non-Covid respiratory viruses, which are dominated numerically by rhinoviruses,” Johnston says. “Everybody wants to get their kids back to school, and everybody wants to get their employees back to work.”

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