The question may seem odd in the midst of a global pandemic, but among people in places with serious mask-wearing and social-distancing measures, and with the luxury to hunker down, it is forgivable to wonder: Will I ever get sick again? In the southern hemisphere, in places like Australia and South Africa, winter flu season came and went without a trace. The western United States is coughing through clouds of smoke, and people everywhere have endured wet-eyed allergy seasons. But over the past 6 months, people were far less likely to get sick sick—at least from respiratory viruses that aren’t called SARS-CoV-2.
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By Eve Sneider
But in some places, that’s started to change. Data from Australia and across Europe indicate a surge of at least one other ailment that has been lying mostly dormant: the common cold. Colds are caused by many viruses, but the culprits, at this point, are largely rhinoviruses. That isn’t especially surprising. Rhinoviruses are ubiquitous bugs that normally spread this time of year as schools and day care centers reopen, which in many places they have. “This is exactly what we’d expect during a normal back-to-school season,” says Catherine Moore, a virologist at Public Health Wales.
But this year isn’t exactly “normal.” What has surprised public health officials is to see the quick return of non-Covid respiratory viruses with social distancing and mask rules still in place. And this year, their return has presented a unique headache for a simple reason: Early symptoms of colds and Covid-19 are virtually indistinguishable.
That has added a new wrinkle to Covid-19 testing. In Britain, where Covid-19 cases are surging amidst a severe shortage of tests, emergency department officials have taken to Twitter to plead with parents to stop bringing mildly ill children—whose symptoms often turn out to be caused by a rhinovirus—in for testing, often in the hopes that a negative Covid-19 test that will allow them to return to school. “Wheeze-tastic,” strapped pediatricians gripe on Twitter. Even in Australia, where Covid-19 cases are hovering near zero in most of the country, the return of other respiratory ailments has strained supplies and complicated efforts to fully quash SARS-CoV-2 by testing for the virus widely.
In some ways, the rise of rhinoviruses is a trial run for Covid-19 testing as more respiratory viruses get back into circulation. The reemergence of colds is less concerning than a surge in influenza that could come this winter. In addition to putting pressure on testing supplies, a bad flu season would tax the same ICU beds, personal protective equipment, and respiratory specialists that health officials hope to save for Covid-19. That could force people back into more strenuous lockdown measures to avoid overburdening the health care system. (Reminder, reader: Get your flu shot.)
Cold season, by contrast, usually exacts its toll quietly. Rhinoviruses are rarely dangerous to anyone but the most medically vulnerable. Their damage is mostly economic, coming in the form of sick days, when people are told to sit tight, drink some fluids, and wait the bug out. Tests are rarely necessary outside of hospitals or surveillance programs, when infections are spotted in a respiratory panel test. But those tests are more expensive and are typically only performed by clinicians after more serious ailments, like the flu, have been ruled out.
Symptoms do not completely overlap, Moore says. A runny nose without fever, for example, is more likely to be a cold, while a case involving a high fever is likely not. But that guidance can be hard to put into practice, especially with kids. “It is incredibly challenging, and I don’t blame anybody who has got a child who is coughing or a bit snotty wanting to get a test,” she says. Still, she says, with Covid-19 tests in short supply, the guidance in the United Kingdom is for the mildly ill to lie low. That’s the same message, she notes, that’s often given during severe flu seasons.
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.”
“The UK seems to have really stumbled,” Mackay says. “They just weren’t prepared for the throughput.” But even in Australia, the arrival of other respiratory viruses has complicated matters, he adds. The country, which has a low number of Covid-19 cases, is taking the opposite approach from the UK. The idea among Australian public health officials is to hunt down every last chain of Covid-19 transmission—embers that could erupt into another true outbreak, like the “second wave” that recently forced the region around Melbourne back into lockdown. That means the government wants to test as widely as possible, even if symptoms are slight. But now rhinoviruses—and increasingly other common viruses, like adenoviruses and RSV—are putting more strain on that system.
Those challenges and more are likely in store for the United States, where the incidence of new Covid-19 cases remains high, and testing resources have been periodically strapped, especially as more schools and businesses reopen. “You’re seeing more opportunities for a savvy pathogen to get transmitted,” Pergam says. “It’s not just rhino. It’s adeno. It’s parainfluenza. It’s RSV. It’s flu. We are thinking that levels will be lower with social distancing and masking, but we don’t yet know for sure.”
Another unknown, he says, is how all those reemerging viruses will intermingle with the new virus, SARS-CoV-2. Viruses compete and augment each other in ways that are largely mysterious to us—they coexist in our bodies and change how our immune systems react to other pathogens. That competition is thought to be one reason why the fall colds are cut off by winter flus, and then burst back again in the spring. Will the progress of Covid-19 be changed by other viruses? It’s a strange universe of viruses out there, and Covid-19 is about to meet the competition.