(CNN)Out of tens of thousands of monkeypox cases around the world this year, there have been a dozen deaths linked to the virus, and for the first time, some of them have been outside Africa, in countries where the virus doesn't usually spread. More than 31,000 cases of monkeypox have been reported globally since January 1, more than 10,000 of them in the United States. Most people have recovered at home with no lasting problems. But doctors are working to understand why monkeypox can be serious and, rarely, fatal. According to the latest numbers from the World Health Organization, there...