The outbreak of Zika virus is "scarier than first thought", US health officials said on Monday.

Scientists are increasingly concerned the virus sweeping through Latin America and the Caribbean causes devastating defects in fetal brains if women become infected during pregnancy.

Now experts are calling for more funds to developing vaccines and treatments, as well as for mosquito control.

"Everything we look at with this virus seems to be a bit scarier than we initially thought," said Dr Anne Schuchat of the Centres for Disease Control and Prevention at a White House briefing.

She added while widespread outbreaks in the US are not expected "we absolutely need to be ready".

Last week, Congress said it would send £412m in funds to help fight the Zika epidemic internationally but experts have warned that is "not enough".

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