Zika virus: President Obama calls for urgent action
US President Barack Obama has called for urgent action against the Zika virus, which has been linked to babies being born with underdeveloped brains.
He said research to develop vaccines and treatments must be speeded up.
The World Health Organization says the virus is likely to spread across nearly all of the Americas.
It has already been found in 21 countries in the Caribbean, North and South America. Symptoms include mild fever, conjunctivitis and headache.
Medics are most worried about the damage the virus can potentially cause to babies in the womb.
Brazil has recorded a huge spike in cases of microcephaly - the condition where babies are born with unusually small heads - and a number of Central and South American nations have asked women to delay pregnancy.
There have been 3,893 reported cases of microcephaly in Brazil since October compared with the previous annual average of just 160 cases.
- A Danish tourist returning home from Latin America has been diagnosed with the virus. Earlier cases in Europe include Germany, Britain and Sweden
- Health officials in the US states of Virginia and Arkansas say two residents who travelled outside America have tested positive for the virus, the AP news agency reported
- Latin America's largest airline, Grupo LATAM, has announced it is waiving cancellation or flight-change fees for pregnant women wanting to cancel flights to affected countries
More on the Zika virus:
Virus 'may spread'
"The president emphasised the need to accelerate research efforts to make available better diagnostic tests, to develop vaccines and therapeutics, and to ensure that all Americans have information about the Zika virus," the White House said in a statement.
Mr Obama was briefed on the potential spread of the virus by senior officials on Tuesday, with one recent study suggesting that the virus may affect regions where 60% of the US population lives.
His spokesman said it was imperative for all Americans to have information about the virus and measures they can take to protect themselves.
US National Institutes of Health Director Dr Francis Collins cited a Lancet study earlier this month in which researchers warned the virus could spread in warmer months along areas of the east and west coasts of the US and much of the Midwest, where about 200 million people live.
The study also shows that nearly 23 million more people live in humid parts of the US where mosquitoes carrying the virus can survive all year round.
"It is now critically important to confirm, through careful epidemiological and animal studies, whether or not a causal link exists between Zika virus infections in pregnant women and microcephaly in their newborn babies," Dr Collins said.
Brazil's government on Tuesday said it would deploy 220,000 soldiers in its fight against the virus. They will go from home to home handing out leaflets on how to avoid its spread.
The announcement came after Health Minister Marcelo Castro said Brazil was "losing badly" in its fight against the virus.
What is Zika virus?
- Spread by the Aedes aegypti mosquito, which also carries dengue fever and yellow fever
- First discovered in Africa in the 1940s but is now spreading in Latin America
- Scientists say there is growing evidence of a link to microcephaly, that leads to babies being born with small heads
- Can lead to fever and a rash but most people show no symptoms, and there is no known cure
- Only way to fight Zika is to clear stagnant water where mosquitoes breed, and protect against mosquito bites