A mosquito-borne virus which has been linked to a surge in cases of children born with brain damage in Brazil could have arrived in the country during the World Cup of 2014, health experts have said.

The surge in cases of the Zika virus has also been linked to unusually wet weather, poor sanitation and a public health service weakened by economic crisis.

Researchers believe the virus - first thought to be relatively innocuous - may have arrived in Brazil during the 2014 football World Cup, carried by visitors from French Polynesia, where an outbreak had just occurred.

Woman in Brazil and Colombia have been warned not to get pregnant until the effect of Zika on unborn children is better understood.

"We are doing this because I believe it's a good way to communicate the risk, to tell people that there could be serious consequences," said Alejnadro Gavira, Colombia's health minister, who called on women to delay pregnancies six to eight months.

The virus is also affecting 20 other countries and territories in the Americas, raising global alarm ahead of the 2016 Olympic Games in Rio de Janeiro.

"The virus found the perfect conditions in Brazil: a very efficient vector that loves human blood, millions of susceptible victims with no antibodies, ideal climate, and lots of places to breed," said Ricardo Lourenço, an expert in tropical infectious diseases at Brazil's Oswaldo Cruz Institute.

The Colombian health ministry has also told state health providers to treat pregnant women who are infected with the Zika virus as high-risk pregnancies, and to provide scans during the entire pregnancy.

The Center for Disease Control and Prevention in the United States has warned pregnant women not to travel to Brazil and 13 countries in Latin America and the Caribbean where the virus is quickly spreading.

But Marcos Espinal, head of the Pan American Health Organization's communicable diseases department, warned that "travel restrictions will not stop the spread of Zika" and it is likely to reach throughout Latin America.

"It's a mosquito that is endemic in the whole of Latin America and the Caribbean, and the population of the Americas was not exposed to the virus, so there's no immunity to it," he said.

Colombia has the second highest infection rate after Brazil, with more than 13,500 people infected with the Zika virus and the disease could hit as many as 700,000.

Unlike dengue, which can cause high fever and join pain, Zika produces symptoms - such as mild fever and rash - that are often so light people don't know they have the disease, health experts say.

But the spread of the virus in Brazil has coincided with a surge in infants born with birth defects - and a possible rise in cases of Guillain-Barre syndrome, a rare condition in which the body's immune system attacks its nerves.

Brazil's Health Ministry said that 3,893 cases of microcephaly, a rare congenital condition in which babies are born with an abnormally small head, have been associated with Zika. The cases have appeared in nearly all Brazilian states. Infants are likely to have contracted the virus from their mothers who were infected while pregnant.

The condition leads to irreversible neurological damage that affects movement and vision.

Although microcephaly has not been definitively connected with Zika, experts believe there is a link, as the virus has been found in brain tissue and amniotic fluid from babies who were born with microcephaly or died in the womb.

In Colombia, there are 560 known cases of pregnant women who are infected with the Zika virus, and who are being closely monitored by health workers. So far no cases of newborns suffering from microcephaly have been recorded.

Three Britons infected with Zika

Three Britons have been infected with Zika virus after travelling to South and Central America, Public Health England (PHE) has said.

The travellers picked up the disease, which is linked to brain deformities in babies, through mosquito bites in Colombia, Suriname and Guyana, PHE confirmed.

Pregnant women have been warned not to travel to countries where the infection has been reported.

PHE said Zika "does not occur naturally" in the UK and added: "As of 18 January 2016, three cases associated with travel to Colombia, Suriname and Guyana have been diagnosed in UK travellers."

A PHE spokesman said the virus is transmitted through mosquito bites and "is not spread directly from person to person".

"A small number of cases have occurred through sexual transmission or by transmission from mother to foetus via the placenta," he added.