The Centers for Disease Control and Prevention last week updated its guidelines for travelers wishing to protect themselves against monkeypox. It was one of his recommendations: “Wear a mask. Wearing a mask can help protect you against many diseases, including monkeypox.
Late Monday evening, this recommendation was removed.
“The CDC removed the mask recommendation from the monkeypox travel health notice because it caused confusion,” the agency said in a statement Tuesday.
However, the agency still says that in countries where monkeypox is spreading, “household contacts and health workers” should consider wearing masks. This guideline also applies to “other people who may be in close contact with someone who has been confirmed to have monkeypox”.
The twist alludes to a little-discussed aspect of the current monkeypox epidemic: the virus can be airborne, at least over short distances. Although airborne transmission is only a small factor in the overall spread, experts said in interviews, there are no firm estimates regarding its contribution.
Since May 13, when the first case of the outbreak was reported, more than a thousand people in 31 countries have been diagnosed with the virus, and at least another thousand cases are under investigation. investigation. As of Tuesday, the United States had recorded 31 cases in 12 states and the District of Columbia.
In previous outbreaks, the majority of cases have been reported in people who have been in 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 patients with monkeypox to wear a surgical mask, “especially those with respiratory symptoms.” It also asks other household members to “consider wearing a surgical mask” when around the person with monkeypox.
Monkeypox is supposed to behave much like its viral cousin, smallpox. In a 2012 study on 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 during a 1947 smallpox epidemic in New York, he wrote, when a patient apparently infected another seven floors away at 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 studying a 2017 outbreak of monkeypox in Nigeria observed cases of transmission in a prison and recorded infections in two health workers who had no direct contact with patients.
At a scientific conference last week hosted by the World Health Organization, several researchers discussed the many unknowns about monkeypox, including its main mode of transmission.
“The actual or dominant route of transmission is very ambiguous, and some of these can be addressed in animal models,” Nancy Sullivan, a researcher at the National Institute of Allergy and Infectious Diseases, said at the conference. “It probably needs to take center stage for some lab research.”
But in briefings with the press and with the general public, health officials did not explicitly address the possibility of airborne transmission or the use of masks for protection.
And in interviews, they highlighted the role of large respiratory droplets that are expelled from infected patients and drift onto objects or people. Monkeypox infection requires “very close and sustained contact,” said Andrea McCollum, the CDC’s top expert on the virus.
“It is not a virus that has transmitted over several meters,” she said. “That’s why we have to be very careful about how to frame this.”
Asked if health officials should make the possibility of airborne transmission more widely known, Ms McCollum said: “It’s a fair point to make, and it’s something we should definitely consider moving forward.”
What to know about the Monkeypox virus
What is monkey pox? Monkeypox is an endemic virus in parts of central and western Africa. It is similar to smallpox, but less serious. It was discovered in 1958, after outbreaks occurred in monkeys kept for research, according to the Centers for Disease Control and Prevention.
The CDC’s quick about-face on masks for travelers concerned about monkeypox was reminiscent of its early denials that the coronavirus was airborne. In September 2020, the agency issued guidelines on airborne transmission of the virus, then abruptly withdrew them days later.
It wasn’t until May 2021 that the agency acknowledged that the coronavirus could “hang in the air for minutes to hours.”
Most of the information about the monkeypox virus has been taken from smallpox studies. Over the past two decades, scientists have studied the spread of smallpox, including its presence in tiny droplets called aerosols, to prepare for its potential use by bioterrorists.
“Most people think smallpox is usually transmitted by large droplets, but it can, for some reason, occasionally be transmitted by small-particle aerosols,” said Mark Challberg, virologist at the National Institute of Allergy. and infectious diseases.
Dr Milton warned that planning for possible airborne transmission of monkeypox was particularly important in hospitals, as precautions to avoid the spread of viruses through aerosols are not universal.
As the monkeypox epidemic continues, many patients isolate themselves at home because their symptoms are mild. Members of these households may need to consider the possibility of airborne transmission, experts said.
There remain many unanswered questions about monkeypox, including why the current outbreak has produced only relatively mild cases. Scientists don’t know if people can transmit the virus even when they don’t have symptoms, how long the virus has been circulating in 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 Congo, the largest of its kind, four out of five pregnant women had miscarriages. The researchers found the virus and viral lesions in the fetuses.