The new coronavirus has infected over 82,000 people and killed over 2,800.
Some preventative measures can help protect you from contracting the virus: Washing hands frequently, avoiding touching your face, and staying away from sick people are all recommended.
But wearing a face mask is not necessarily an effective option for everyone.
Here's how to determine whether you should wear a mask.
If you're wondering whether you need a medical face mask to protect you from the new coronavirus, you probably don't.
The Centers for Disease Control and Prevention (CDC) only recommends masks for a select group of people: Those in a region currently experiencing an outbreak, healthcare workers treating coronavirus patients, and anyone who experiences flu-like symptoms.
For the rest of us, preventative measures like washing your hands frequently, avoiding touching your face, and staying away from sick people are all probably more effective than wearing a mask.
Since the outbreak began Wuhan, China, in December, more than 82,000 people have been infected and at least 2,800 have died. Cases have been recorded in 49 other countries. Health agencies are working to contain outbreaks in South Korea, Italy, and Iran, while the US is also preparing for an uptick in cases.
The coronavirus spreads via droplets when people are within about 6 feet of one another. In healthcare settings, it also can spread via exposure to infected patients' saliva, phlegm, blood, and respiratory droplets.
Here's who needs to wear a face mask and who doesn't
There are two kinds of masks: surgical masks and N95 respirators.
N95 respirators filter out most airborne particles from the air, preventing wearers from breathing in particles down to 0.3 microns in diameter. These types of masks are often used when air quality is poor due to wildfire smoke or pollution.
When worn correctly, N95 respirators block out at least 95% of small airborne particles, so the respirators can filter out some droplets carrying coronavirus. The coronavirus itself measures between .05 and 0.2 microns in diameter, according to an article in The Lancet.
Surgical masks, meanwhile, are designed to keep droplets and splatter from passing from a person's mouth to nearby surfaces or people. They're primarily meant as a physical barrier to keep healthcare providers or sick people from spreading their own mouth-borne germs. Research has shown that even people who get the coronavirus but don't show symptoms can spread it.
If you live in an outbreak zone, you should wear a mask.
In China's Hubei province, where Wuhan is located, local authorities have mandated that residents wear masks when they go outside, but they haven't stipulated whether people wear surgical masks or respirators.
There are currently 65,596 cases in the province, and all residents are under quarantine.
In South Korea, which has over 1,260 coronavirus cases (the largest number outside of mainland China), the government has posted notices encouraging residents to wear masks in public and telling them that it is a "must" on public transportation.
If you're a healthcare worker treating coronavirus patients, it's standard procedure to wear personal protective gear, including masks.
Protective gear varies based on the level of risk providers face, but the CDC recommends gowns, masks or respirators, googles or face shields, and gloves.
Healthcare workers need masks to protect themselves from the infectious germs they're exposed to in hospitals. If they come down with an infection themselves, masks also prevent them from spreading their germs to vulnerable patients.
In China, at least 3,000 healthcare workers have gotten the new coronavirus.
If you're caring for someone sick at home, you should also wear a face mask. All others in the house should wear masks as well.
Patients who have tested positive for the coronavirus should wear masks in healthcare settings.
Patients being treated in hospitals in China all wear masks, though some hospitals have reported resource shortages.
Similarly, the CDC has directed healthcare professionals in the US to put surgical face masks on patients with any respiratory symptoms, as well as on people who recently traveled to China or had contact with someone who did.
Health agencies recommend that anyone experiencing flu-like symptoms wear masks when around other people.
The coronavirus causes flu-like symptoms: fever, cough, and shortness of breath. If you're experiencing any of these, the CDC recommends that you stay home and away from other people. If you live with others, stay in a separate room and use a different bathroom if possible.
When you are around others, the CDC suggests wearing a face mask as a precautionary measure to avoid spreading germs.
The agency asks anyone with coronavirus symptoms to call ahead before visiting a hospital or doctor's office so that the staff can prepare properly.
If you're a healthy person who's not in an outbreak zone and you don't work in a medical setting, you don't need a mask.
'Only wear a mask if a healthcare professional recommends it'
The CDC says it "does not recommend that people who are well wear a face mask to protect themselves from respiratory illnesses, including COVID-19."
The agency's guidance is: "You should only wear a mask if a healthcare professional recommends it. A face mask should be used by people who have COVID-19 and are showing symptoms. This is to protect others from the risk of getting infected."
Because hospitals around the world face shortages of personal protective equipment, especially masks, individuals who don't need them but stock up anyway could contribute to these shortages, potentially hindering healthcare response and effectiveness.
For the average person outside of an outbreak zone, the CDC says the best precautions are the standard, everyday ways to avoid all germs: wash your hands frequently, don't touch your face, and regularly disinfect surfaces.