GENEVA: The World Health Organization (WHO) said on Wednesday that $56 million were needed to combat the Zika virus until June, including for the fast-tracking of vaccines, diagnostics and research studies into how it spreads.

The funds, including $25 million for the WHO and its regional office, would also be used to control the mosquito-borne virus that has spread to 39 countries, including 34 in the Americas, and has been linked to birth defects in Brazil.

"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," WHO director-general Margaret Chan said in the WHO Strategic Response Framework and Joint Operations Plan issued in Geneva.

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

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.

The United Nations health agency 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.

Brazil is investigating the potential link between Zika infections and more than 4,300 suspected cases of microcephaly, a condition marked by abnormally small head size that can result in developmental problems.

Researchers have confirmed more than 460 of these cases as microcephaly and identified evidence of Zika infection in 41 of these cases, but have not proven that Zika can cause microcephaly.

The WHO noted that "existing scarce evidence indicates that there may be a risk of sexual transmission" of Zika virus, as well as a risk of it persisting in semen and urine.

"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, including pregnancy-related fluids, and potential sexual transmission, and mother-to-child transmission, the WHO said.