Measles resurgence in the United States
Measles was declared eliminated from the United States in 2000, by the World Health Organization (WHO) due to the success of vaccination efforts. However, it continues to be reintroduced—especially when unvaccinated people travel out of the United States to places where measles is present.
Source: Wikipedia — Measles resurgence in the United States (CC BY-SA 4.0)