GENEVA: Declaring that the Zika virus is “spreading explosively,” chief of the World Health Organisation announced it will hold an emergency meeting of independent experts on Monday to decide if the virus outbreak should be declared an international health emergency.

At a special meeting Thursday in Geneva, WHO Director-General Dr Margaret Chan said the virus - which has been linked to birth defects and neurological problems - is becoming more of a threat.

Chan said although there was no definitive proof that the Zika virus was responsible for a spike in the number of babies being born with abnormally small heads in Brazil, “the level of alarm is extremely high.”

She also noted a possible relationship between Zika infection and Guillain-Barre syndrome, which can cause temporary paralysis.

“The possible links, only recently suspected, have rapidly changed the risk profile of Zika from a mild threat to one of alarming proportions. The increased incidence of microcephaly is particularly alarming, as it places a heart-breaking burden on families and communities,” Chan said.

The virus is strongly suspected of causing birth defects and may infect 3-4 million people in the Americas, including 1.5 million in Brazil, a World Health Organization expert said on Thursday.

Marcos Espinal, head of communicable diseases at PAHO -- the WHO’s Americas arm -- said a study would soon be published suggesting a correlation between Zika and microcephaly -- babies born with small heads and brains -- in Brazil.

“We don’t know yet if this virus crosses the placenta and generates or causes microcephaly. We think it plays a role.

There’s no doubt about that,” he told the WHO’s executive board meeting in Geneva.

Brazil urged its neighbors Wednesday to unite in fighting the Zika virus, blamed for a surge in brain-damaged babies, as airlines offered refunds to pregnant mothers afraid to travel to the region.

As alarm rose over the latest world health scare, US President Barack Obama called for faster research on the quick-moving virus, which has infected travelers from the United States and Europe.

Brazil has been the country hardest hit by the outbreak of the mosquito-borne virus, which is blamed for a sharp rise in infants born with microcephaly, or abnormally small heads.

The outbreak is particularly concerning officials as the country prepares to host the Olympics, which will bring hundreds of thousands of travelers from around the world to Rio de Janeiro in August.

Zika has spread to some 20 countries in Latin America and the World Health Organization (WHO) expects it to spread to every country in the Americas except Canada and Chile.

Denmark and Switzerland joined a growing number of European countries to report Zika infections among travelers returning from Latin America.

There is currently no specific treatment for Zika and no way to prevent it other than avoiding mosquito bites.

Brazilian President Dilma Rousseff said she had asked a summit of the 33-member Community of Latin American and Caribbean States (CELAC) to launch “cooperative action in the fight against the Zika virus.”

An American Airlines spokesman said the company was offering refunds to pregnant women with flights booked to Brazil and 10 other countries and territories affected by the virus.

Another US airline, Delta, said some its passengers may also qualify for a refund or a change to their tickets.

US President Barack Obama has called for faster research on the virus.

Obama on Tuesday urged better diagnostic tests and the development of vaccines and treatments against the virus, which the World Health Organization has said is likely to spread throughout the Americas.

As of now, there is no vaccine or medicine to treat Zika virus, and no way to prevent it other than by trying to avoid mosquito bites.

— Agencies