As monkeypox outbreak swells, experts offer guesses as to why Europe has seen unprecedented spread

A handful of additional cases have been reported in the U.S., Canada and Australia since Wednesday.The growing case tally has raised questions among disease experts about the nature of monkeypox's transmission, since many of the patients have no history of travel to Africa or known exposure to an infected person."How they initially got infected and why it's all over the place is still a mystery," said Dr. Stuart Isaacs, an associate professor of medicine at the University of Pennsylvania. Monkeypox isn't considered a sexually transmitted infection, but it could be passed during sexual encounters, experts said.Many of the recent cases in Europe are among men who have sex with men, and a Friday alert from the Centers for Disease Control and Prevention suggested that some recent cases started out with lesions around the anus and genitals."I'm guessing that sexual transmission will be high on the list of potential culprits," said Dr. Grant McFadden, director of the Biodesign Center for Immunotherapy, Vaccines and Virotherapy at Arizona State University.McFadden, Isaacs and several other experts offered their early ideas about to how and why the new outbreak has swelled.McFadden said the genetic sequence of the monkeypox virus that has infected people in Europe looks relatively run-of-the-mill.