WASHINGTON (AFP) - US President Barack Obama has called for faster research on the quick-moving Zika virus, which is spread by mosquitoes and has been linked to a rise in birth defects in Brazil.
Obama on Tuesday urged better diagnostic tests and the development of vaccines and treatments against the virus, which the World Health Organization has said is likely to spread throughout the Americas.
As of now, there is no vaccine or medicine to treat Zika virus, and no way to prevent it other than by trying to avoid mosquito bites.
Obama was briefed on the situation by top science experts in the US government, including the US Centres for Disease Control and Prevention, Health and Human Services, and the National Institutes of Health, according to a White House statement.
The CDC also expanded its travel warning for pregnant women and those considering becoming pregnant to avoid 24 areas in Latin America and the Caribbean that have seen cases of Zika virus.
Now, travellers are advised to postpone visits to the US Virgin Islands and the Dominican Republic, along with Puerto Rico, Barbados, Bolivia, Brazil, Cape Verde, Colombia, Ecuador, El Salvador, French Guiana, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Saint Martin, Samoa, Suriname and Venezuela.
There have not yet been any cases of local transmission of Zika virus within the United States, although infected travellers have returned to the country after visiting other areas.
However, a recent study in The Lancet suggests that Zika virus could reach regions of the United States in which 60 per cent of the population lives, or some 200 million Americans.
"This highlights the need for NIH and its partners in the public and private sectors to intensify research on Zika virus and to look for new ways to treat the disease and prevent its spread," NIH director Francis Collins wrote on his blog.
Zika virus is spread to people primarily through the bite of an infected Aedes species mosquito, according to the CDC.
Symptoms are usually mild and may include fever, rash, joint pain and conjunctivitis.
However, the virus can pass from a pregnant women to her fetus, and global health authorities are concerned by an apparent link between Zika virus and nearly 4,000 cases of babies born with unusually small heads - a condition known as microcephaly - in Brazil.
Collins stressed that more research is needed to prove if there is any cause-and-effect between the Zika virus and brain defects.
Meanwhile, experts are also concerned about "reports in French Polynesia and Brazil of a possible connection between Zika infection and Guillain-Barré syndrome, a mysterious condition in which the immune system attacks part of the peripheral nervous system," said the NIH director.
He added that US health authorities are "mobilizing swiftly" to respond to Zika, and researchers at the National Institute for Allergy and Infectious Diseases are already "working on vaccine candidates to prevent Zika virus from infecting people." The first documented case of human infection with Zika virus was in 1968, according to the World Health Organization.
Zika is named after a forest in Uganda where it was first detected in rhesus monkeys 1947.