乌鸦传媒

The CDC removed a recommendation to wear a mask from its monkeypox guidance for travelers earlier this week, saying it "caused confusion," according to a statement from the agency shared with 乌鸦传媒.

The guidance : "Wear a mask. Wearing a mask can help protect you from many diseases, including monkeypox."

But that statement on CDC's "Travel Health Notices" for monkeypox.

"Late Monday CDC removed the mask recommendation from the monkeypox Travel Health Notice because it caused confusion," the CDC statement said.

The statement added that in "countries where there is a current monkeypox outbreak, CDC continues to recommend masking in high-risk situations including for household contacts and healthcare workers, or for other people who may be in close contact with a person who has been confirmed with monkeypox."

The retraction comes as World Health Organization (WHO) Director-General Tedros Adhanom Ghebreyesus, PhD, that the "risk of monkeypox becoming established in non-endemic countries is real."

However, it's not too late to turn things around, WHO officials said. There's "still a window of opportunity to prevent the onward spread of monkeypox in those who are at highest risk right now" and bring the virus under control, Rosamund Lewis, MSc, WHO's technical lead on monkeypox, said during the briefing.

Yet scientists have raised legitimate concerns about the virus becoming endemic in the U.S. by potentially establishing itself in an animal population here. If that happens, the U.S. could face repeated human outbreaks, according to

There's currently no animal reservoir outside of Africa, where it's thought that rodents are the primary animal host, according to Science.

Questions have also been raised about modes of transmission in monkeypox, and a noted that the virus can be airborne, "at least over short distances" -- which is no surprise to infectious disease experts. While airborne transmission is not thought to be a major driver of spread, the Times reported that "there are no firm estimates regarding how much it contributes."

It's widely accepted that the primary mode of human-to-human transmission is through very close contact, especially directly with lesions; and that, at least in endemic areas, it's much more commonly transmitted from an animal to a human host.

That's one reason why Grant McFadden, PhD, a virology expert at Arizona State University, said masks probably aren't needed at a population level yet.

"Masks do make sense for people in close contact to monkeypox-infected individuals, but they should not be needed for general use by the public for protection against this disease," McFadden told 乌鸦传媒 via email.

The CDC did not respond to additional 乌鸦传媒 questions on transmission and masking, but the agency is now tracking and . As of Thursday June 9, there were 45 cases in 16 states, according to the CDC tracker. On Wednesday, the WHO confirmed more than 1,000 cases in 29 countries outside West and Central Africa.

Jennifer McQuiston, DVM, deputy director of the Division of High Consequence Pathogens and Pathology at the CDC, told reporters during an Association for Health Care Journalists fellowship gathering on the CDC campus earlier this week that Canada has shifted to a preventive vaccine strategy in certain cases.

"They recently made a switch, because they have a big outbreak happening in Montreal with a lot of cases ... and it probably is that they had so many cases that they couldn't effectively do contact tracing," McQuiston said.

Earlier this week, Quebec province in Canada reported a total of 90 confirmed cases of monkeypox, and began offering a smallpox vaccine to certain close contacts of people who had been infected, . So far, 813 people have been vaccinated, according to the report.

"If we see something like that happening in the United States," McQuiston said, "we might make a similar decision."

She added that CDC scientists are developing risk models to inform CDC as to when flipping that switch and making the vaccine more widely available would be appropriate.

Amanda D'Ambrosio contributed to this report.

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