As fear about the deadly new coronavirus spreads in China, face masks have disappeared from store shelves and sold out online. At least two Chinese provinces now require them to be worn in public. Factories that make the masks in China are operating 24 hours a day to meet the demand.
But medical experts say the effectiveness of masks at preventing the spread of the coronavirus is limited. Many of the masks people are wearing do little to protect them, and even the most effective have to be fitted and worn properly to have any benefit.
They can even be harmful if the discomfort of wearing them leads people to touch their faces or a potentially contaminated mask more frequently.
"The likelihood that any of these are going to protect anyone in these environments is minimal," said Bruce Ribner, medical director of Emory University Hospital's Serious Communicable Diseases Unit. "Wearing these things can in some ways be worse than not wearing one."
Medical experts say the best ways for people to avoid infection are to wash their hands often, and avoid touching their eyes, mouths and noses.
Still, masks have become hard to find both inside and outside of China, with online platforms, including Amazon, selling out at times. There are shortages at hospitals and medical centers, where millions of masks are required daily, not only for working with coronavirus patients but also for other infectious diseases, surgeries and basic medical care.
Dr. Ribner said Emory has been receiving daily calls from other medical centers who purchase supplies on an as-needed basis asking if they have any to spare.
3M Co., a major supplier, said it has increased production in response to the outbreak.
"We are ramping up production in all of our facilities around the world, including in China, to full capacity. 24/7 production to meet the demand," 3M Chief Executive Mike Roman said in an interview on Tuesday.
Foshan Nanhai Beautiful Nonwoven Co., a Chinese maker of masks, surgical gowns and drapes, is running its factories 24 hours a day to meet demand set by the government of Hubei province, according to Deng Weixiong, a general manager of the company.
The company, which has seven facilities in southern and eastern China and about 3,000 employees, had to recruit more than 400 temporary workers to ramp up production during the Lunar New Year holiday to cover for existing workers who had left to spend time with their families, Mr. Deng said.
Chinese authorities say they still believe masks of any kind are worthwhile. In Jiangxi province, southeast of the city of Wuhan where the virus originated, an employee at a provincial health commission hotline said that neighborhood committees have been instructed to dissuade anyone from going out in public without a mask.
This is to "avoid cross-infection in places where there is a large flow of people and dense crowds," the person said.
"Don't believe what the experts say, listen to the government first," added an employee at a similar hotline in Hubei province, which includes Wuhan.
With masks in short supply, many people have resorted to wearing whatever they can find. Qi Qi, a 20-year-old freelancer in the northwestern Chinese city of Harbin, has taken to wearing a pink polyurethane mask when she goes out, even though she knows it isn't meant for protecting against disease.
"I couldn't find the proper mask in Harbin. They are out of stock everywhere," Ms. Qi said. "At least I am wearing something, right?"
Health experts say the most likely way to contract a disease like the coronavirus--a family of pathogens responsible for several respiratory illnesses, including both common colds and severe acute respiratory syndrome, or SARS--is through the eyes and nose. Often, that happens when infected droplets from coughs or sneezes land on a surface and get picked up by healthy people who touch the surface, and then their faces.
Such droplets can typically last from one to four hours once they land on surfaces, which is why health professionals recommend people wash their hands often and avoid touching their faces.
If used properly, masks can at least help block some large droplets from sneezes and coughs. They can also prevent wearers from touching their noses and mouths if they are careful. But paper or polyurethane foam masks, also known as surgical masks, don't filter out smaller particles.
Reusable respirator masks, also called N95 masks, are considered by some to be best, if they are fitted by a professional. In such cases they fit tightly, making it harder for particles to get through. Prices have surged and various online platforms have vowed to keep costs down.
But many users don't wear the masks properly, and they aren't designed to be worn for hours at a time. People who try to wear them for long periods often find them uncomfortable and try to adjust them, touching their faces in the process.
In the medical profession, N95 masks are generally only used by doctors working with airborne viruses like measles, says Aaron E. Glatt, chairman at the department of medicine at Mount Sinai South Nassau in Oceanside, N.Y. and a spokesman for the Infectious Disease Society of America. Coronaviruses generally involve larger droplets that don't stay suspended in the air.
Besides, "if you put it in your purse it's potentially going to contaminate everything in your purse," said Dr. Glatt.
Despite those concerns, the coronavirus outbreak has amplified social pressure to wear masks, to the point where there is a stigma associated with those who don't--especially in Asia.
Surgical-style face masks have become increasingly popular in the region since the outbreak of SARS in late 2002. Many people wear them when suffering from common colds or coughs, but their use has expanded to include combating the pollution that hovers over many Asian cities.
They have become something of a fashion accessory for many younger people, who wear them to hide blemishes, make their faces appear smaller or mimic pop idols like Lu Han, a Chinese entertainer.
Over the past week, doctored photos featuring characters from Mickey Mouse to Buddha--all wearing surgical masks--have started making the rounds on WeChat, a messaging app with more than 1.1 billion global monthly active users.
Posters depicting Cultural Revolution-period characters wearing 3M's version of the N95 mask have been circulated widely on Chinese social media. Some of the posters made by social media users feature red characters in big fonts and messages as dramatic as the political slogans of the 1960s.
"If one person is infected (with the virus) then the entire family will collapse; all family wealth will belong to the relatives," reads one. Another says "Mask or medical ventilator? It is your option to pick one of either."
Yang Jie, Raffaele Huang, Reddy Zhao, Austen Hufford and Nina Trentmann contributed to this article.