The five-year-old entered the Central American nation earlier this month with his family and stayed at hotels in San Jose and Santa Teresa during the holiday.

But the boy and his parents, aged 30 and 35, were ‘placed in isolation’ in Puntarenas Hospital after a private doctor was asked to examine the youngster’s ‘rash’.

His mother, who is also unvaccinated, is understood to have revealed that other children in her son’s school had previously contracted the disease.

A search is on for people he may have come into contact with including at the hotels, on the Air France flight over on February 18 and in his homeland, health officials say.