GENEVA (Reuters) - The World Health Organization (WHO) said on Wednesday that $56 million would be needed until June to fund a strategy to combat the Zika virus which has spread to 39 countries and has been linked to birth defects in Brazil.

A health worker fumigates as part of preventive measures against the Zika virus and other mosquito-borne diseases, at the cemetery of Presbitero Maestro in Lima, Peru, February 12, 2016. REUTERS/Mariana Bazo

The funds sought, including $25 million for the WHO, would be used to fast-track vaccines, carry out diagnostics and research into how the mosquito-borne virus spreads, as well as virus control, the WHO said.

Last year, the United Nations health agency was forced to admit its handling of an Ebola virus epidemic, which killed more than 11,300 in two years, most of them in West Africa, had been inadequate. Public health expert Lawrence Gostin said on Wednesday the WHO’s reaction to the Zika emergency was again “too little, too late”.

The WHO declared the Zika outbreak a global public health emergency on Feb 1, noting its association with two neurological disorders, microcephaly in babies and Guillain-Barre syndrome that can cause paralysis.

Director-General Margaret Chan will travel to Brazil from Feb 22-24 to review Zika-related measures supported by WHO and will meet the health minister, a WHO spokeswoman said.

“Possible links with neurological complications and birth malformations have rapidly changed the risk profile for Zika from a mild threat to one of very serious proportions,” Chan said in the WHO’s strategy paper.

But Gostin, a professor at Georgetown University in Washington, warned that the WHO had “grossly underestimated” the task as the virus was likely to spread to many other regions from the Americas.

States with major Zika outbreaks could incur up to a 10 percent loss in GDP, as was “likely” in Brazil, he said in a statement.

“The WHO put out financing estimates during Ebola, which were also far from adequate, and it repeatedly raised (them) as the epidemic unfolded. It is doing the same thing now with Zika.”

The WHO had failed to learn the “fundamental lesson” from Ebola, Gostin said.

“That lesson is that mobilizing funding in the midst of a global emergency will always be too little, too late.”

SMALL STEP FORWARD

The WHO expects the funds to come from states and other donors and said that in the meantime it has tapped a new emergency contingency fund for $2 million for initial operations.

There is no treatment, but hopes of developing a vaccine against Zika took a small step forward on Wednesday as U.S. biotech firm Inovio Pharmaceuticals Inc said its experimental shot had induced a robust and durable response in mice.

Brazil said on Wednesday it is investigating the potential link between Zika infections and more than 4,443 suspected cases of microcephaly, a condition marked by abnormally small head size that can result in developmental problems.

Researchers have confirmed 508 of these cases as microcephaly. The ministry said last week that 41 of the confirmed cases of microcephaly had shown links to Zika infection but did not update the figure.

The WHO noted that “existing scarce evidence indicates that there may be a risk of sexual transmission” of Zika virus.

“There is currently very little evidence of mother-to-child transmission; however, intra-uterine infections seem to be associated with subsequent neurological conditions in the child.”

Research studies are needed to assess the presence of the Zika virus in semen and other body fluids, and potential sexual transmission, and mother-to-child transmission, the WHO said.