Neymar da Silva Santos, centre, and his Brazilian teammates celebrate winning the tournament in Rio in 2013 / Getty

Scientists point to match between Tahiti and Uruguay in Recife as a probable source of the outbreak in South America

The Zika virus was probably introduced into South America during a football tournament in 2013 when supporters from a French Polynesian national team visited the north-east of Brazil, the epicentre of the epidemic which has affected at least 30,000 people, a study has found.

A genetic analysis of the virus from different regions around the world has pointed to a single introduction between May and December 2013 from French Polynesia, where an outbreak was taking grip for the first time during 2013 and 2014.

Scientists believe that a football tournament known as the Confederations Cup, which took place in June 2013, could have been the catalyst for the Brazilian outbreak, the biggest the world has known, following a significant increase in air passengers from French Polynesia.

The researchers point to a match between the French Polynesian national team of Tahiti and Uruguay which was played at a stadium in Recife in the north-eastern region of Brazil, near the epicentre of the epidemic, which has also seen an unprecedented increase in the number of cases of babies born with microcephaly – the small-brain congenital disorder linked with Zika.

The same study, published in the journal Science, also found that the 4,000 or more cases of microcephaly seen in the north-east of Brazil best correlate with the introduction of Zika into the region – although the data are not yet strong enough to confirm the Zika virus is the cause, the scientists said.

“We looked at broad-scale patterns of human movement and focussed on air passengers who travelled to Brazil from countries that reported Zika since 2012. From late 2012 onwards, there was a 50 per cent rise in the number of passengers travelling to Brazil from countries with Zika,” said Professor Oliver Pybus of Oxford University.

The genetic analysis of the Zika virus show that the closest strain to the one found in Brazil is the one that caused the earlier epidemic in Polynesia, which probably arrived from South East Asia. The very first known Zika virus was isolated in East Africa in 1947, from where it spread across Africa to Asia.

“Although the American outbreak virus is most closely related to a strain from French Polynesia, it’s also possible that Zika was introduced separately to the Americas and French Polynesia from South East Asia,” Professor Pybus said.

“To better understand Zika transmission history, we need more information about the epidemiology and genetic diversity of Zika viruses in South East Asia,” he said.