Scientists who have monitored numerous outbreaks of monkeypox in Africa say they are baffled by the disease’s recent spread in Europe and North America. Cases of the smallpox-related disease haven’t previously been seen among people with no links to central and West Africa. But in the past week, Britain, Spain, Portugal, Italy, the United States, Sweden and Canada have all reported infections, mostly in young men who hadn’t traveled to Africa. On Friday, France, Germany, Belgium and Australia all confirmed their first cases of monkeypox. One of the theories British health officials are exploring is whether the disease is being sexually transmitted.