A growing outbreak of mpox (monkeypox) in the Democratic Republic of the Congo (DRC) raises concerns about wider spread. The virus has two subtypes, Clade I and Clade II, with the former having a higher fatality rate. Historically, mpox was an uncommon disease linked to contact with wild animals. In contrast, the Clade II global outbreak in 2022 was mainly driven by sex between men. Clade I mpox began rising in the DRC last year. There appear to be concurrent outbreaks, one largely affecting children and the other involving sexual transmission among men and women. Clade I mpox has not been detected in the United States, but low-level transmission of Clade II continues, with 750 cases reported this year. The CDC recommends two doses of the Jynneos vaccine—which protects against both clades—for people at risk, including sexually active gay men, transgender people, HIV-positive people and those on PrEP. Only about 25% of eligible individuals have received both doses, and most recent cases involved people who were not fully vaccinated.