evidence: During 1970–2015, 11 cases of YF were reported in people from the United States and Europe who traveled to West Africa (6 cases) or South America (5 cases); 8 (73%) died. Only 1 traveler had a documented history of YF vaccination; that traveler survived. Starting in 2016, the number of travel-associated YF cases increased substantially, primarily because of outbreaks in Angola and Brazil. During 2016–mid-2021, >37 travel-associated cases were reported in unvaccinated travelers who were residents of nonendemic areas or countries, including ≥15 European travelers and 1 American traveler to Peru.