You might be infected with the coronavirus and not ever know it.

(Getty Images)

Research suggests that up to 25% of those who become infected with the coronavirus may not show symptoms. The high percentage of infected yet asymptomatic people could help explain the spread of the coronavirus across the U.S., according to Dr. Robert Redfield, director of the Centers for Disease Control and Prevention. Redfield discussed the possible mode of transmission during a recent interview with a National Public Radio affiliate in Atlanta. "This helps explain how rapidly this virus continues to spread across the country," Redfield said during the interview.

At the beginning of the outbreak, public health officials said they believed the primary mode of transmission occurred when people showing symptoms of COVID-19 – the disease caused by the coronavirus – coughed or sneezed on a person. Public health authorities initially said members of the general public had no need to wear face masks.

Fever.

Fatigue.

Sore throat.

Body aches.

A persistent, dry cough.

The CDC shifted its stance on whether members of the general public should wear masks outside after it published the research on presymptomatic transmission.

In late February and early March, at the outset of the coronavirus outbreak in the U.S., the CDC, the U.S. Surgeon General and the U.S. Department of Health and Human Services urged members of the general public to not wear masks.

On Feb. 29, the Twitter account of the U.S. Surgeon General tweeted: "Seriously people - STOP BUYING MASKS!"

The tweet added that masks are "NOT" effective in preventing the general public from catching the coronavirus. It noted that if health care providers treating coronavirus patients can't get masks to care for sick patients, it would put them and the communities they work in at risk.

But the new research published by the CDC suggests that presymptomatic and asymptomatic people infected with the coronavirus could pass the virus to other individuals.

The study focused on seven clusters of people with COVID-19 in Singapore involving patients who were probably infected by presymptomatic or asymptomatic individuals. As of March 16, researchers found, 10 of 157 cases of COVID-19 that were acquired locally – more than 6% – were attributed to presymptomatic or asymptomatic transmission.

"Presymptomatic transmission might occur through generation of respiratory droplets or possibly through indirect transmission," researchers wrote. "Speech and other vocal activities such as singing have been shown to generate air particles, with the rate of emission corresponding to voice loudness."

Wearing a mask in public may help cut down on coronavirus transmission from people who aren't symptomatic, says Dr. Carl J. Fichtenbaum, a professor in the Division of Infectious Diseases at the University of Cincinnati College of Medicine.

It's important to keep in mind how wearing a mask in public helps stop the transmission of the coronavirus, Fichtenbaum says. Unless you're wearing a medical grade N95 mask meant for use by health care professionals who are treating people with COVID-19, donning the face gear is unlikely to shield you from being infected.

Rather, wearing a mask minimizes the amount of aerosol droplets you emit into the air, which in turn could prevent other people from being infected, Fichtenbaum says. Aerosolized droplets that people emit by breathing or talking can hang in the air indoors for up to three hours.

"Wearing a mask minimizes the odds that you'll infect someone else," he says. "Broad use of masks is a good idea. It protects the people around you. If we're all filtering (by using masks), we're decreasing the amount of secretions and aerosol that comes out of our nose and mouth."

Stopping the spread of the coronavirus is in everyone's interest -- including your own, he notes.

The CDC has not mandated that people wear any particular type of mask.

There are several different types of face masks available, including:

Respirators, like the N95 masks worn by health care professionals.

Surgical masks.

Cloth masks.

Paper masks.

Bandannas made of cotton and other fabrics.

While it's a good idea to also wear a mask when you're outdoors, the odds of emitting infectious droplets, or of becoming infected by aerosolized virus, are generally far lower when you're outside, Fichtenbaum says.

Air circulates outside, dissipating droplets emitted by people when they're breathing or talking.

You're generally safe from being infected with the coronavirus when you're outdoors, so long as you practice social distancing and stay at least 6 feet away from the nearest person. "It's not like you're going to randomly walk into a cloud of infected air (outdoors)," Fichtenbaum says. "You should be fine outside, so long as you don't stand 2 feet away from someone who's talking into your face."

Infected and Asymptomatic: How Long Will It Last?

Some people who become infected with coronavirus may never develop symptoms, and some will only develop mild symptoms, says Dr. Eyal Zimlichman, chief medical officer and chief innovation officer at Sheba Medical Center near Tel Aviv, Israel.

Public health authorities recommend that people who test positive for the coronavirus remain in self-isolation, or quarantine, for 14 days. Symptoms typically develop within that time frame.

In the U.S., with rare exceptions, only people who are showing symptoms of COVID-19 are being tested for the coronavirus.