Monkeypox can also be airborne

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Monkeypox can also be airborne

The Centers for Disease Control and Prevention last week updated its guidance for travelers wanting to protect themselves from monkeypox. This was one of her recommendations: “Wear a mask. Wearing a mask can help protect you from many diseases, including monkeypox.”

That recommendation was deleted late Monday evening.

“The CDC removed the mask recommendation from the monkeypox travel health notice because it caused confusion,” the agency said in a statement Tuesday.

But the agency still says that in countries where monkeypox is spreading, “household contacts and healthcare workers” should consider wearing masks. This policy also applies to “other people who may be in close contact with a person confirmed to have monkeypox.”

The turnaround points to a little-discussed aspect of the current monkeypox outbreak: the virus can be airborne, at least over short distances. While airborne transmission is only a small factor in overall spread, experts said in interviews, there are no firm estimates of how much it contributes.

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 a thousand more cases are being investigated. As of Tuesday, the United States had recorded 31 cases in 12 states and the District of Columbia.

In previous outbreaks, most 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 monkeypox patients to wear a surgical mask, “especially those who have respiratory symptoms.” It also urges other household members to “consider wearing a surgical mask” if they are around the person with monkeypox.

Monkeypox is believed to behave similarly to its viral cousin, smallpox. In a 2012 review of smallpox transmission, Dr. Donald Milton, a virus expert at the University of Maryland, reports several cases of airborne transmission.

It was the only plausible explanation, he wrote, during a smallpox outbreak in New York in 1947, when one patient apparently infected another seven floors away in a hospital. Then, in 1970, a single patient infected several others on three floors of a hospital in Meschede, Germany, aided by air currents in the building.

And scientists studying a 2017 monkeypox outbreak in Nigeria observed cases of transmission inside a prison and registered infections in two healthcare workers who were not in direct contact with patients.

At a scientific conference organized by the World Health Organization last week, several researchers discussed the many unknowns about monkeypox, including its primary mode of transmission.

“It’s very unclear what the true or dominant mode of transmission is, and some of that can be studied in animal models,” Nancy Sullivan, a researcher at the National Institute of Allergy and Infectious Diseases, said at the conference. “Probably that needs to come to the fore for some of the laboratory research.”

But in briefings with the press and the general public, health officials have not specifically addressed the possibility of airborne transmission or the use of masks for protection.

And in interviews, they emphasized the role of large respiratory droplets expelled by infected patients, floating on objects or people. Monkeypox infection requires “really close, sustained contact,” said Andrea McCollum, the CDC’s lead expert on the virus.

“This is not a virus that has been transmitted over several meters,” she said. “So we have to be very careful how we do it.”

Asked whether health officials should raise awareness of the possibility of airborne transmission, Ms McCollum said: “That’s a fair point and we should definitely consider moving forward.”

The CDC’s quick about-face on masks for travelers concerned about monkeypox was reminiscent of their early denials that the coronavirus was in the air. In September 2020, the agency released guidance on airborne transmission of the virus and abruptly withdrew it just days later.

It was only in May 2021 that the agency acknowledged that the coronavirus could “remain suspended in the air for minutes to hours.”

Most information about the monkeypox virus comes from studies of smallpox. For the past two decades, scientists have studied how smallpox spreads, including its presence in tiny droplets called aerosols, in preparation 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 Institute of Allergy and Infectious Diseases.

dr Milton warned that planning for potential airborne transmission of monkeypox in hospitals is particularly important because precautions to avoid aerosol spread of virus are not universal.

As the monkeypox outbreak continues, many patients are isolating at home because their symptoms are mild. According to experts, members of these households may need to consider the possibility of airborne transmission.

Many unanswered questions about monkeypox remain, including why the current outbreak has produced only relatively mild cases. Scientists don’t know if people can transmit the virus without symptoms, how long the virus circulates in communities, and if it can be transmitted in 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 out of five pregnant women miscarried. The researchers found the virus and viral lesions in the fetuses.

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