In the early days of the pandemic, one of the scariest and most surprising features of SARS-CoV-2 was its stealth. Initially assumed to transmit only from people who were actively sick—as its predecessor SARS-CoV did—the new coronavirus turned out to be a silent spreader, also spewing from the airways of people who were feeling just fine. After months of insisting that only the symptomatic had to mask, test, and isolate, officials scrambled to retool their guidance; singing, talking, laughing, even breathing in tight quarters were abruptly categorized as threats.
Three years later, the coronavirus is still silently spreading—but the fear of its covertness again seems gone. Enthusiasm for masking and testing has plummeted; isolation recommendations have been pared down, and may soon entirely disappear. “We’re just not communicating about asymptomatic transmission anymore,” says Saskia Popescu, an infectious-disease epidemiologist and infection-prevention expert at George Mason University. “People think, What’s the point? I feel fine.”
Although the concern over asymptomatic spread has dissipated, the threat itself has not. And even as our worries over the virus continue to shrink and be shunted aside, the virus—and the way it moves between us—is continuing to change. Which means that our best ideas for stopping its spread aren’t just getting forgotten; they’re going obsolete.
When SARS-CoV-2 was new to the world and hardly anyone had immunity, symptomless spread probably accounted for most of the virus’s spread—at least 50 percent or so, says Meagan Fitzpatrick, an infectious-disease transmission modeler at the University of Maryland’s School of Medicine. People wouldn’t start feeling sick until four, five, or six days, on average, after being infected. In the interim, the virus would be xeroxing itself at high speed in their airway, reaching potentially infectious levels a day or…
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