One of the most frustrating aspects of COVID-19 is that the virus is most commonly spread when an infected individual is asymptomatic—either because they have yet to develop symptoms or they are one of the lucky 40% who never will. Due to the nature of asymptomatic spread and the long incubation period, the virus is nearly impossible to contain. Since the beginning of the pandemic, researchers have been attempting to figure out why some people, who never develop symptoms, spread the virus, while others who become ill, don't. Now, a new study out of South Korea claims to have found the answer.

Asymptomatic People Carry Virus in Nose, Throat and Lungs

The study, published Thursday in JAMA Internal Medicine, claims that asymptomatic people are infected with just as much of the virus in their nose, throat, and lungs, as even those who get sick, and for as long. The new study analyzed samples of 193 symptomatic and 110 asymptomatic people with a median age of 25, measuring the virus's genetic material. They also tracked their temperatures, monitored other symptoms, and measured the amount of virus present in their lungs, noses, and throats.

Of those who were initially asymptomatic patients, 89—about 30%—remained healthy, while 21 developed symptoms. Both groups, both symptomatic and asymptomatic, boasted similar viral loads during their infections. However, while asymptomatic people became virus-free around Day 17, those with symptoms didn't shed the virus until Day 19 or 20. Keep in mind that they weren't necessarily contagious at this point, but fragments of the virus were still in their system.

"Many individuals with SARS-CoV-2 infection remained asymptomatic for a prolonged period, and viral load was similar to that in symptomatic patients; therefore, isolation of infected persons should be performed regardless of symptoms," authors of the study suggest.
40% Have No Symptoms, Says Fauci

Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases recently estimated that 40% of those infected with the virus remain without symptoms, warning that they were still responsible for spreading it.

"The good news about Covid-19 is that about 40 percent of the population have no symptoms when they get infected," Dr. Fauci said. But "even though you are likely not going to get symptoms, you are propagating the outbreak, which means that you're going to infect someone, who will infect someone, who then will have a serious consequence."

Until a vaccine is widely available, do everything you can to prevent getting—and spreading—COVID-19: Wear a face mask, get tested if you think you have coronavirus, avoid crowds (and bars, and house parties), practice social distancing, only run essential errands, wash your hands regularly, disinfect frequently touched surfaces, and to get through this pandemic at your healthiest, don't miss these 37 Places You're Most Likely to Catch Coronavirus.