'Somewhere between 25% and 50%' of people who get the coronavirus may show no symptoms but still be contagious, Fauci says. Here's the latest research on asymptomatic carriers.

At least one-third of the world is under some type of lockdown because of the coronavirus pandemic, as governments urge social distancing to stymie the virus' spread.

That's because the COVID-19 virus is insidious.

"There's significant transmission by people not showing symptoms," Stephen Morse, an epidemiologist at Columbia University, told Business Insider.