The Centers for Disease Control and Prevention updated its guidelines last week for travelers who want to protect themselves from monkeypox. This was one of his recommendations: “Wear a mask. Wearing a mask can help protect you from many diseases, including monkeypox.”
On Monday night, this recommendation was removed.
“The CDC removed the recommendation for masks from the health warning of monkeypox travel because it caused confusion,” the agency said in a statement Tuesday.
However, the agency still says that in countries where smallpox is spreading, “domestic contacts and health workers” should consider wearing masks. This guideline also applies to “other people who may be in close contact with a person who has been confirmed with smallpox.”
The change indicates a little-discussed aspect of the current smallpox outbreak: the virus can be transmitted through the air, at least over short distances. While air transmission is only a small factor in the overall spread, experts said in interviews, there are no firm estimates of how much it contributes.
Since the first case of the outbreak was reported on May 13, more than a thousand people in 31 countries have been diagnosed with the virus, and at least a thousand more cases are being investigated. On Tuesday, the United States reported 31 cases in 12 states and the District of Columbia.
In previous outbreaks, most cases were reported in those who had close contact with an infected patient or animal. But in some cases, airborne transmission was the only explanation for the infections.
Elsewhere on its website, the CDC still urges monkeypox patients to wear a surgical mask, “especially those with respiratory symptoms.” He also asks other members of the household to “consider wearing a surgical mask” when they are in the presence of the person with smallpox.
The monkey’s smallpox is supposed to behave much like its viral cousin, the smallpox. In a 2012 review of smallpox transmission, Dr. Donald Milton, a virus expert at the University of Maryland, described several cases of airborne transmission.
It was the only plausible explanation for a smallpox outbreak in 1947 in New York, he wrote, when it appears a patient infected another seven floors in a hospital. Then, in 1970, a single patient infected several others on three floors of a hospital in Meschede, Germany, helped by drafts in the building.
And scientists who studied a monkeypox outbreak in 2017 in Nigeria observed cases of transmission inside a prison and recorded infections in two health workers who had no direct contact with patients.
At a scientific conference organized last week by the World Health Organization, several researchers discussed the many unknowns about the monkey’s smallpox, including its main mode of transmission.
“It’s very ambiguous what the true or dominant route of transmission is, and part of that can be addressed in animal models,” Nancy Sullivan, a researcher at the National Institute of Allergy and Infectious Diseases, told the conference. . “This probably needs to be at the forefront of some of the lab research.”
But in briefings with the press and the general public, health officials have not explicitly addressed the possibility of airborne transmission or the use of masks for protection.
And in the interviews, they emphasized the role of large respiratory droplets that are expelled from infected patients and move towards objects or people. Monkeypox infection requires “really close sustained contact,” said Andrea McCollum, the CDC’s leading expert on the virus.
“This is not a virus that was transmitted in several meters,” he said. “That’s why we have to be very careful about how we frame this.”
When asked if health officials should make the possibility of airborne transmission more widely known, Ms McCollum said: “It’s a fair point, and we should definitely consider moving forward.”
What you need to know about the monkeypox virus
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What is the smallpox of the monkey? Smallpox is an endemic virus in parts of central and western Africa. It is similar to smallpox, but less severe. It was discovered in 1958, after outbreaks of monkeys kept for research, according to the Centers for Disease Control and Prevention.
What are the symptoms? The monkeypox creates a rash that begins with flat red markings that rise and fill with pus. Infected people may also have a fever and body aches. Symptoms usually appear between six and 13 days, but can take up to three weeks after exposure and can last between two and four weeks. Health officials say smallpox vaccines and other treatments can be used to control an outbreak.
How contagious is it? The virus spreads mainly through body fluids, skin contact and respiratory droplets, although it can occasionally pass through the air, at least over short distances. It does not usually cause major outbreaks, although this year it has spread in unusual ways and among populations that have not been vulnerable in the past.
Do I have to worry? The virus is likely to spread during sexual intercourse, but the risk of transmission in other ways is low. Most people have mild symptoms and recover within a few weeks, but the virus can be fatal in a small percentage of cases. Studies also suggest that older adults may have some protection against smallpox vaccines from decades ago.
The CDC’s rapid change of face in masks for travelers worried about monkeypox was reminiscent of its early denials that the coronavirus was transmitted through the air. In September 2020, the agency published a guide on the transmission of the virus through the air and then abruptly withdrew it a few days later.
It wasn’t until May 2021 that the agency acknowledged that the coronavirus could be “suspended in the air for minutes or hours.”
Most of the information on smallpox virus has been obtained from smallpox studies. For the past two decades, scientists have been studying how smallpox spreads, including its presence in small droplets called aerosols, in order to prepare for its potential use by bioterrorists.
“Most people think that smallpox is usually transmitted by large droplets, but for whatever reason, it can occasionally be transmitted by small particle aerosols,” said Mark Challberg, a virologist at the National Allergy Institute. and Infectious Diseases.
Dr. Milton warned that planning for the possible transmission of smallpox by air was especially important in hospitals, because precautions to prevent the spread of viruses through aerosols are not universal.
As the monkeypox outbreak continues, many patients are isolating themselves at home because their symptoms are mild. Members of these households may need to consider the possibility of airborne transmission, experts said.
Many unanswered questions remain about monkeypox, including why the current outbreak has only produced relatively mild cases. Scientists do not know if people can transmit the virus even in the absence of symptoms, how long the virus has been circulating in the communities and whether it can be transmitted through semen or vaginal secretions.
There is evidence that a pregnant woman can transmit the monkeypox virus to her fetus. In an observational study of 216 patients in the Democratic Republic of the Congo, the largest of its kind, four of the five pregnant women had miscarriages. The researchers found the virus and viral lesions in the fetuses.