Zika US
Dr Anthony Fauci (R) and Dr Anne Schuchat speak about the Zika virus at the White HouseKevin Lamarque/Reuters

Leading public health officials in the US have warned that the Zika virus is "scarier" than initially thought and urged Congress to pass $1.9bn (£1.3bn) in emergency funding requested by the Obama administration in February. The aedes aegypti mosquito which transmits the virus was previously thought to be present in 12 US states, but that figure now stands at 30.

Fears that the virus could spread are increasing with the possibility of hundreds of thousands of cases cropping up in the US territory of Puerto Rico, according to a Reuters report. "Everything we look at with this virus seems to be a bit scarier than we initially thought," said Dr Anne Schuchat of the US Centers for Disease Control and Prevention during a White House briefing on 11 April.

"Most of what we've learned is not reassuring," Schuchat said. "And so while we absolutely hope we don't see widespread local transmission in the continental US, we need the states to be ready for that." She added that a greater range of birth defects have been attributed to the disease.

Despite asking for nearly $2bn in emergency funding for Zika preparedness, Washington has been using the remaining $589m from the Ebola virus fund. If Republican-led Congress does not clear the path to provide the funding, money for research into malaria, tuberculosis and a universal flu vaccine could be used instead.

"I don't have what I need right now," said Dr Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases. "When the president asked for $1.9 billion, we needed $1.9 billion," added Fauci, warning that the Ebola virus fund was just a temporary stopgap.

According to Schuchat, hundreds of thousands of people could infected by Zika in Puerto Rico with possibly hundreds of babies affected by the virus. The latest Zika outbreak has spread across 23 countries in the Americas and is linked to microcephaly, a condition where babies are either born with small heads or the head stops growing after birth, which could cause developmental problems.