For Saturday's declaration, WHO Director-General Tedros Adhanom Ghebreyesus acted as a "tie breaker" after members of the International Health Regulations Emergency Committee failed to come to a consensus once again. Monkeypox is a virus that's related to smallpox, but it's much milder. It has been endemic in Western and Central Africa for nearly 50 years, but the scale of this outbreak is unprecedented. Right now, Dr. Ghebreyesus added, the virus seems to be largely spreading between men who have sex with men, and the majority of new cases are in Europe.