The prevailing theory is that their immune systems fight off the virus so efficiently that they never get sick.

“That is a tremendous mystery at this point,” says Donald Thea, an infectious disease expert at Boston University’s School of Public Health. But scientists aren’t sure why certain people weather Covid-19 unscathed. They occur with the regular flu, and probably also featured in the 1918 pandemic, according to epidemiologist Neil Ferguson of Imperial College London. They don’t feel a thing.Īsymptomatic cases are not unique to Covid-19. But in addition to these pre-symptomatic patients, the relentless silent spread of this pandemic is also facilitated by a more mysterious group of people: the so-called asymptomatics.Īccording to various estimates, between 20 and 45 percent of the people who get Covid-19 - and possibly more, according to a recent study from the Centers for Disease Control and Prevention - sail through a coronavirus infection without realizing they ever had it.

Instead of staying home in bed, they may be out and about, unknowingly passing the virus along. O ne of the reasons Covid-19 has spread so swiftly around the globe is that for the first days after infection, people feel healthy.

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