NEW YORK — Genetic analysis of recent cases of monkeypox suggests there are two distinct strains in the U.S., health officials said Friday, raising the possibility that the virus has been circulating undetected for some time.
Federal health officials said that many U.S. cases were caused by the same strain as recent cases in Europe, but a few samples show a different theme. Each song had been seen in U.S. cases last year before the recent international outbreak was identified.
According to Jennifer McQuiston of the Centers for Disease Control and Prevention, analysis of many more patients will be needed to determine how long monkeypox has been circulating in the U.S. and elsewhere.
“I think it’s certainly possible that there have been cases of monkeypox in the United States that went under the radar before but not to a great extent,” she told reporters on Friday. However, she added, “Community-level transmission can occur” in parts of the U.S. where the virus has not yet been identified.
The CDC said it is trying to increase its work on finding infections, and it is likely more cases will be reported.
The findings mean the outbreak will likely be difficult to contain, said Dr. Angela Rasmussen, a virologist at the University of Saskatchewan.
It is not clear how long infections have been happening and where. Some conditions may have been misdiagnosed as something else.
“We don’t really have a good idea of how many cases there are,” Rasmussen said.
Monkeypox is endemic to parts of Africa where humans have been infected through bites from rodents or small animals. It usually does not spread easily among people.
But last month, cases started popping up in Europe and the United States. Many – but not all – of those who contracted the virus had traveled internationally, and health officials in many countries are investigating.
By Friday, the U.S. had identified at least 20 cases in 11 states. Hundreds of other issues have been found in other countries, many apparently related to sexual activity at two recent European raves.
So far, many reported cases outside of Africa have been in men who have sex with men, but health officials emphasize that anyone can get monkeypox. A heterosexual woman is one of the U.S. cases under investigation, officials said.
The disease usually begins with flu-like symptoms and swelling of the lymph nodes, followed by a rash on the face and body.
No deaths from monkeypox have been reported in the U.S. or Europe. But that could change if infections occur in more vulnerable people, such as very young children or those with weakened immune systems, Rasmussen said.
She raised another concern: Even if outbreaks among humans are contained, it’s possible the virus could take over the U.S. rodent population — either through pets or unwanted rodents in homes.
“It’s not ruled out,” Rasmussen said.
Also, on Friday, the CDC released an analysis of 17 of the first reported U.S. According to the report, fourteen teens had traveled internationally to 11 different counterparts. The mean age was 40 years, and all but one identified themselves as having sex with men. According to the report, f
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