No Costa Rican has contracted the measles since 2006. An unvaccinated tourist unknowingly traveled while contagious and is now in quarantine.
The CDC lists 10 US states as reporting active measles infections and suggests children be vaccinated.
A French family arrived in Costa Rica last Monday and put an end to Costa Rica's measles-free status: No citizen there has contracted the disease since 2006, and the last time a foreigner brought it to the country was in 2014. The Independent reports that a 5-year-old boy was taken to a doctor due to a rash; it turns out children at his school have been diagnosed with measles and that he hadn't been vaccinated against it. The Costa Rica Star reports he tested positive for measles and is currently being quarantined at a hospital in Puntarenas. Officials are working to determine who may have been in contact with the child during his flight and as the family traveled in San Jose and Santa Teresa; an infected person is generally contagious for about eight days.