Barack Obama will ask the US Congress for more than $US1.8 billion in emergency funds to combat the rapid spread of the mosquito-borne Zika virus.

In an announcement on Tuesday (AEDT), the White House said the money would be used to expand mosquito control programs, speed development of a vaccine, develop diagnostic tests and improve support for low-income pregnant women.

Zika is spreading in Central and South America, the Caribbean, Southeast Asia and the Pacific. While most people who catch the virus experience few symptoms, there are concerns the unborn babies of infected pregnant women may be at risk of a birth defect that shrinks their brains and skulls, possibly causing brain damage.

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In a television interview to coincide with the funding push, the US president said “there shouldn’t be panic”, but that the virus’ spread should be taken seriously.

“But there shouldn’t be panic on this, this is not something where people are going to die from it. It is something we have to take seriously,” Mr Obama told CBS News.

His funding request will include $US200 million for vaccine research; $US250 million for Zika-affected Puerto Rico, which is administered by the US; and $US335 million for the US Agency for International Development to fund public health efforts in the Americas.

There are no vaccines or treatment for Zika and none even undergoing clinical studies, as the disease had previously been viewed as relatively benign. 
Most infected people develop either no symptoms or mild ones like a fever and skin rashes.

Scientists are working to definitively prove a strongly suspected causal link between Zika and babies born with microcephaly, meaning they have abnormally small heads and can suffer developmental problems. The research began after a huge rise in such birth defects last year in Brazil at the same time the virus took hold there.

Most of the money sought by Obama, who faces pressure from Republicans and some fellow Democrats to act decisively on Zika, would be spent in the United States on testing, surveillance and response in affected areas.

“As spring and summer approach, bringing with them larger and more active mosquito populations, we must be fully prepared to mitigate and quickly address local transmission within the continental US, particularly in the Southern United States,” the White House said in a statement.

There have been 50 confirmed cases of Zika in the continental United States among people who had travelled to affected areas, according to federal health officials.

The Pan American Health Organization reported 26 countries and territories with local Zika transmission.

The Australian government recently promised up to A$500,000 to the Pacific to help stop the spread of the virus after an “epidemic” was declared in Tonga.

-with AAP