Dr. Anthony Fauci of the National Institutes of Health just outside Washington DC said on Monday he didn't want to be "an alarmist," but appealed for more funds to be made available to fight the Zika virus.

Fauci particularly emphasized the need for the development of vaccines and treatments against Zika.

The Obama administration has been investing funds left over from the fight against Ebola to finance research into Zika, but there hasn't been nearly enough spending on research on the virus. But Fauci said that the $589 million now available was a "temporary stopgap" and "not enough for us to get the job done."

A comprehensive strategy would, however, involve the spending of almost four times that figure, which President Obama has asked for in Congress. Little is known about Zika - how long it may hide out in the human body, the degree of risk of sexual transmission, or the full list of diseases it may cause.

Zika in Puerto Rico and the rest of the US

Zika cases in the US territory of Puerto Rico in the Caribbean have jumped to 436. About 60 pregnant women were reportedly infected with Zika. The US Centers for Disease Control and Prevention (CDC) is trying to help Puerto Rico fight Zika.

Experts are trying to determine if the mosquito-borne virus might trigger a paralyzing condition known as Guillain-Barre syndrome and microcephaly, which leads to babies being born with small heads and sometimes brain damage. There are indications of five possibly Zika-linked cases of Guillain-Barre syndrome.

Dr. Anne Schuchat, a deputy director of CDC, meanwhile told reporters that the first vaccine candidate for the virus should be available in September. She also announced that the type of mosquito which carries the virus was more present in the US than previously known. She said what authorities were learning about the virus was "scarier than we initially thought."

Zika to come to Europe?

Disease experts have also warned that Zika may find its way into virus-carrying mosquitoes in Europe, but also stress that any outbreaks were likely to be small.

"I would say that the southern part of the United States and southern Europe are definitely at risk," tropical medicine professor Eskild Petersen of Denmark's Aarhus University said at a conference in Amsterdam. But he stressed that the risk should not be exaggerated.

"It is a disease which in the vast majority of cases is a mild viral disease."

ss/rc (AP, Reuters, AFP)