A vaccine for the Zika virus, a mosquito-borne illness that has surged through Latin America and been linked to birth defects in children in the region, is still years away, US health officials have warned.

Authorities said they are not expecting any large outbreaks in the US, but have begun to prepare for mosquito control in potentially affected areas, with fears that clement spring weather could bring a spate of cases north of the Rio Grande.

There is currently no cure or vaccine for the virus which, in most people, causes mild symptoms.

Up to 30 million Americans are expected to travel to Zika virus affected areas during the spring break holiday this month, prompting officials to advise people to be aware of the risks to pregnancy.

Dr Anthony Fauci from the US National Institutes of Health said vaccine trials could begin mid-year.

“If it looks like it’s safe we’ll go to the next stage. [We are] unlikely to have a vaccine that’s widely available for a few years, but we certainly can get the initial steps,” he said.

US President Barack Obama has asked Congress for $US1.8 billion ($AU2.5 billion) to combat the virus.

The White House said fresh cash is needed to fund mosquito control programs, vaccine research and other “essential strategies” to combat the virus and help “ongoing preparedness efforts”.

Zika is not deadly but in Latin America has been linked to a rapid rise in the number of children born with microcephaly — abnormally small heads and brains.

While Mr Obama called for more funds, he also urged calm.

“The good news is this is not like Ebola, people don’t die of Zika — a lot of people get it and don’t even know that they have it,” he told television channel CBS.

“There appears to be some significant risk for pregnant women or women who are thinking about getting pregnant.

“We don’t know exactly what the relations there are but there is enough correlation that we have to take this very seriously.”

Pharmacies starting to sell out of repellents

The hardest hit country is Brazil, which hosts the Summer Olympics starting in August.

Fear of catching the virus has become a national obsession, dabbing this year’s carnival extravaganza with a large dollop of mosquito repellent.

Firms report sales of spray have increased 800 per cent from December 2015 to January 2016.

Pharmacies report they are starting to sell out of some repellents.

There, the virus has been linked to Guillain-Barre syndrome, a neurological disease that can cause paralysis in humans.