May 18, 2022 – The CDC says it’s concerned about an unusual outbreak of monkeypox in the U.K.

The outbreak could spread beyond U.K. borders, the agency said, particularly because there appears to be some undetected spread of the virus.

“We do have a level of concern that this is very different than what we typically think of from monkeypox,” Jennifer McQuiston, DVM, a senior CDC official, told STAT News, the outlet reported Tuesday.

“And I think we have some concern that there could be spread outside the U.K. associated with this,” she said.

U.S. health officials are monitoring six Americans for potential monkeypox infection after they shared a flight with a British patient who tested positive for the virus. They sat within a three-row radius of the patient on a flight from Nigeria to the U.K. on May 4. The U.S. patients likely don’t have the virus but will be monitored for 21 days, McQuiston told STAT.

Seven confirmed cases and one probable case have been reported in the U.K. since early May, which is unusual and considered a large number since human monkeypox cases are rare, especially outside of West and Central Africa.

The first U.K. patient had recently traveled to Nigeria, where monkeypox is endemic, but the others appear to have gotten the virus in the U.K., STAT reported. None of the people who were infected domestically have known connections with the traveler, and the timing suggests that the traveler wasn’t the source of the other cases.

The domestic cases have also emerged among two groups with no links to each other, STAT reported. Two of the confirmed cases and the possible case are part of a family unit, and the other four confirmed cases are among people who are gay, bisexual, or other men who have sex with men. Among those, three are from London and the fourth is from Newcastle, though all four were likely infected in London.

U.K. health authorities still aren’t sure how the patients contracted the monkeypox virus, STAT reported. Transmission typically occurs through droplets, though direct contact with lesions or bodily fluids can also lead to transmission.

With two unconnected clusters, more than one chain of transmission may be circulating in the U.K., STAT reported, which means that other cases may exist that haven’t yet been detected. It could also mean that the virus has traveled elsewhere, moving outside of the U.K.

Human monkeypox cases outside Africa are rare, though some cases have popped up in other parts of the globe in recent years. Two appeared in the U.S. in 2021, both related to travel from Nigeria, according to the CDC.

Monkeypox has symptoms that are like those of smallpox, which was declared eradicated in 1980, but are typically milder. People often get flu-like symptoms and a rash, particularly on the palms of the hands.

There aren’t specific drugs or vaccines for monkeypox cases, though the smallpox vaccine has been used in the past for some outbreaks. During a 2003 outbreak in the U.S., 47 people in six states got the virus due to imported exotic animals, particularly pet prairie dogs, according to the CDC.

In the U.K., public health authorities have alerted sexual health clinics to look for signs of the distinctive rash, since cases have come about among people who are gay, bisexual, or other men who have sex with men. In the U.S., the CDC is thinking about sending out a health alert to medical professionals and sexually transmitted infection clinics as well.

“There’s a lot of travel between the U.K. and the United States and other global areas,” McQuiston told STAT News. “So I think our concern is that given that you do have four cases among men who have sex with men, that we probably need to be thinking about messaging to our STI clinics … about what to be on the lookout for, what to be alert for.”

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STAT News: “CDC expresses concern about possibility of undetected monkeypox spread in U.K.”

CDC: “Monkeypox in the United States.”

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