“Seriously people,” the surgeon general said on Twitter, warning that a run on the masks could risk a shortage harmful to public health professionals.
The surgeon general on Saturday urged the public to stop buying masks, warning that it won’t help against the spread of the coronavirus but will take away important resources from health care professionals.
“Seriously people — STOP BUYING MASKS!” the surgeon general, Jerome M. Adams, said in a tweet on Saturday morning. “They are NOT effective in preventing general public from catching #Coronavirus, but if health care providers can’t get them to care for sick patients, it puts them and our communities at risk!”
The plea comes as panicked consumers rush to buy masks online, including so-called N95s, a surge that has led to price gouging and counterfeit products.
In another tweet, Mr. Adams said the best way to protect against the virus is to wash hands regularly, and for those who are feeling ill to stay home.
Health officials around the world have been imploring the public to stop buying masks if they are healthy or not caring for someone who is ill. Medical professionals need a large supply of the masks because they are in direct contact with infected patients and must change their masks repeatedly.
“There are severe strains on protective equipment around the world,” said Dr. Michael J. Ryan, executive director of the health emergency program at the World Health Organization, during a briefing on Friday. “Our primary concern is to ensure that our front line health workers are protected and that they have the equipment they need to do their jobs.”
Dr. Ryan said masks primarily prevent a person from giving the disease to someone else.
“There are limits to how a mask can protect you from being infected,” he said. “The most important thing everyone can do is wash your hands, keep your hands away from your face and observe very precise hygiene.”
The W.H.O.’s guidelines recommend that health workers use surgical masks to cover their mouths and noses but the Centers for Disease Control and Prevention has instructed them to wear masks known as N95s, which are thicker, fit more tightly around the mouth and nose, and block out much smaller particles than surgical masks do.
Both masks help prevent the spread of droplets from a person’s cough or sneeze, but medical specialists have said that for average members of the public, they are generally not effective.
A person is more likely to get infected by touching contaminated surfaces than from a droplet traveling through the air.
Air can also get in around the edges of the masks, particularly flat surgical masks. Health care workers who wear N95 masks as part of their jobs are required to undergo a fit test at least once a year to ensure that there are no gaps around their mouths.
Most people are unlikely to know how to wear these masks and could accidentally contaminate themselves if they touch the outside of the mask when they remove it and then touch their face.
“Not having a mask does not necessarily put you at any increased risk of contracting this disease,” Dr. Ryan said.
But the message has not stopped people from buying the masks, particularly the N95s, which are usually inexpensive and popular with construction workers and painters.
“You know what a mask costs?” said Mike Bowen, the executive vice president of Prestige Ameritech, an N95 mask manufacturer in North Richland Hills, Texas. “Listen to this: A Class 2 medical device, you can buy two of them for the price of a gumball.”
He added: “They’re cheap. They’re automated. They’re not handmade.”
But on Amazon, sellers have been advertising masks for at least $10 each. One seller advertised 160 masks for $800, a deal that was no longer available as of Saturday.
Vice President Mike Pence seemed to address the shortage during a White House press briefing with President Trump on Saturday.
Mr. Pence, whom Mr. Trump appointed to coordinate the government’s response to the coronavirus outbreak, said the administration would have “40 million masks available today.”
The government has contracted with the multinational manufacturing giant 3M to produce 30 million more masks a month, Mr. Pence said.
Robert Redfield, director of the Centers for Disease Control and Prevention, told the House Foreign Affairs Committee on Thursday that it was critical that masks remain available for doctors and nurses who were caring for those affected by the virus and for people tending to loved ones with the illness.
“There is no role for these masks in the community,” he said. “These masks need to be prioritized for health care professionals that as part of their job are taking care of individuals.”
Dr. Redfield’s comment came after an exchange with Representative Chrissy Houlahan, a Democrat of Pennsylvania, who asked how people should be preparing, including whether they needed to stock up on food or prescription medication.
“Not at this time,” he said.
“Should people be afraid?” Ms. Houlahan asked.
“No,” he replied.
“Should you wear a mask if you’re healthy?” she asked.
“No,” Dr. Redfield said.
