Cases of a rare disease called monkeypox, which is caused by a less serious virus of the smallpox virus, are emerging worldwide, including in the United States. The virus was first identified in 1958, and it is endemic to many countries in Africa. But, how did the virus spread to countries such as Canada, Spain, and the United States? What are the symptoms of infection with this virus? Dr. Sanjay Gupta, CNN’s chief medical correspondent, explains everything you need to know regarding monkeypox.