An unvaccinated French boy is suspected of having reintroduced measles to Costa Rica after the Central American country had been free of the disease for five years.

It is unclear why the five-year-old French tourist had never received a measles jab, but the arrival of the highly contagious, potentially deadly disease in a country that has been measles-free since 2014 is likely to increase anxiety about the effects of the worldwide anti-vaccine movement.

The reintroduction of measles to Costa Rica comes a month after the World Health Organisation (WHO) warned that “vaccine hesitancy” is in the top 10 of the worst health threats facing humanity in 2019.

Costa Rica’s health ministry said the French five-year-old had arrived in the country with his parents on 18 February.

The Costa Rica Star reported that the boy and his mother had not been vaccinated. The parents were said to have consulted a private doctor in Costa Rica about their son’s “rash”, and confirmed that other children who had attended the boy’s school in France had come down with measles.

The famous faces of the anti-vaccine movement Show all 7 1 /7 The famous faces of the anti-vaccine movement The famous faces of the anti-vaccine movement Charlie Sheen Sheen fought a legal battle against ex-wife Denise Richards to try and block her from vaccinating their children. Richards of course won and Sheen was reportedly so bitter that he paid the paediatrician bill entirely in nickels Getty The famous faces of the anti-vaccine movement Gwyneth Paltrow Paltrow's "health and wellness" company Goop hosted a notorious anti-vaccine speaker at their 2018 Goop Summit Getty The famous faces of the anti-vaccine movement Rob Schneider Schneider demanded the freedom to decline vaccination Getty The famous faces of the anti-vaccine movement Jenny McCarthy McCarthy has claimed that "people are dying from vaccinations", believes that her son caught autism from a vaccine and has pushed her opinions on the topic publicly for many years AFP/Getty The famous faces of the anti-vaccine movement Bill Maher Maher has long spoken against vaccines sating on Larry King live that "a flu shot is the worst thing you can do." His stance appears to stem from a distrust of government AFP/Getty The famous faces of the anti-vaccine movement Alicia Silverstone In Silverstone's book The Kind Mama, she wrote that "there is increasing anecdotal evidence from doctors who have gotten distressed phone calls from parents claiming their child was ‘never the same’ after receiving a vaccine." Getty The famous faces of the anti-vaccine movement Andrew Wakefield Godfather of the anti-vax movement, disgraced doctor Andrew Wakefield famously published a report in the medical journal Lancet claiming a link between the MMR vaccine and autism in 1998. The Lancet retracted the report in 2010 and Wakefield was struck off the medical register PA

The health ministry said the boy was now being treated and kept in strict isolation at the Monseñor Sanabria Hospital in the port town of Puntarenas.

The health ministry is seeking to establish who may have come into contact with the infected child, including during his flight, at a San José hotel where the family stayed for one night and at the beach village of Santa Teresa, near Puntarenas, where they were having their holiday.

The French authorities have also been informed about the boy’s illness, so they can track whether anyone else has been infected in the European country.

Costa Rica’s health ministry said the last time one of its own citizens had measles was in 2006. Before the five-year-old French boy fell ill, the last case of measles being imported to Costa Rica had been in 2014.

The health ministry issued a statement saying: “Our country enjoys very good vaccination coverage in general. However, in order to avoid particular cases and their possible complications, it is important that those in charge of minors ensure that children have the complete vaccination scheme.

Support free-thinking journalism and attend Independent events

“The ministry of health requests that if you know of someone who has symptoms of measles (fever, nasal congestion, cough, conjunctivitis, skin rash that starts in the head and expands through the body to the feet, reaching the hips around the second day) it is vital that they notify the health authorities as soon as possible.

“The above symptoms are of particular importance for people who in the previous 20 days have been in countries with measles transmission or in contact with an eventual imported case.”

The measles-struck town battling anti-vaccine propaganda

The WHO has said that despite the availability of a safe and cost-effective vaccine, there were 110,000 measles deaths globally in 2017, mostly among children under the age of five.

The WHO has warned that the number of measles cases worldwide had risen by more than 30 per cent between 2016 and 2017, with increases recorded in rich European countries like Germany where vaccination coverage had previously been high.

Martin Friede, the WHO’s director of immunisation, vaccines and biologicals, said that “supposed experts making accusations against the vaccine without any evidence” had adversely affected parents’ decision-making.

The WHO also warned that “complacency” was stopping some parents from getting their children vaccinated.

Placing vaccine hesitancy – the reluctance or refusal to get immunised – among the world’s top 10 health threats, the WHO warned: “Some countries that were close to eliminating measles have seen a resurgence.”

In the UK a wave of anxiety about the MMR (measles, mumps and rubella) vaccine was triggered in 1998 when Dr Andrew Wakefield published a paper linking the jab to autism in children.