U.S. health officials are investigating a case of monkeypox in Massachusetts, carrying out contact tracing as the CDC tracks multiple cases in several countries.
Health officials said the patient, who is being treated at Massachusetts General Hospital, is a man who had recently travelled to Canada.
Health officials there said they are investigating 17 suspected cases in Montreal.
In the past two weeks, monkeypox has been identified in Portugal, Spain, and Britain. On Thursday, France said it was investigating its first suspected case in the Paris area.
"Until this year there have been very few cases ever reported around the world of this. But then this year we've had this unprecedented cluster of cases that occurred," said Jimmy Whitworth, a professor of international public health at the London School of Hygiene and Tropical Medicine.
Monkeypox is a rare viral infection similar to human smallpox, and mostly occurs in west and central Africa. Symptoms include fever, headaches and a distinctive bumpy skin rash starting on the face and spreading to the rest of the body.
While the global spread is causing some concern among public health officials, the virus does not transmit easily.
"The reservoir is in small mammals, usually rodents in West African and Central African forest. And so people get infected if they come into contact in some way with those animals. It can then spread from person to person. But it's not very efficient at transmitting. And so what we normally see is maybe one or two people get infected from that case and then it dies out because it's not very infectious within the human population."
Whitworth said while most people will recover in a few weeks, others may be hospitalized, and in some cases, the virus can be fatal.