There are fears the virus is now being carried by the common mosquito
The Zika virus is "spreading explosively", the head of World Health Organisation (WHO) has warned amid fears it may be carried by the common mosquito.
Speaking at a meeting of WHO members states, Director-General Dr Margaret Chan said the level of alarm over the virus has become "extremely high".
The mosquito-borne virus has been linked to a steep increase in the number of babies born with severe birth defects, including abnormally small heads, across the Americas.
"A causal relationship between Zika virus infection and birth malformations and neurological syndromes has not yet been established, but is strongly suspected," the WHO chief said.
"The possible links, only recently suspected, have rapidly changed the risk profile of Zika, from a mild threat to one of alarming proportions," she added.
She has called an emergency meeting to discuss whether the outbreak qualifies as an international public health emergency on February 1st in Geneva.
The WHO warning comes as scientists in Brazil said it is possible the virus is carried by the common mosquito.
Up until now, it was thought the Aedes aegypti mosquito, which is confined to the tropics, was solely spreading the virus.
Cases of the Zika virus have so far been reported in 23 countries and territories.
According to US media, five people in the New York area alone have tested positive for the virus. All of them are understood to have contracted it while travelling abroad.
The WHO says it will also prioritise the development of vaccines and new tools to control mosquito populations, as well as improving diagnostic tests.
The European Centre for Disease Surveillance and Control (ECDC) issued an updated risk assessment earlier this week.
It says El Salvador, Venezuela, Colombia, Brazil, Suriname, French Guiana, Honduras, Mexico, Panama and Martinique are currently experiencing a rapidly evolving Zika virus epidemic with an increasing or widespread transmission.
While Bolivia, Guyana, Ecuador, Guadeloupe, Guatemala, Paraguay, Puerto Rico, Barbados, Saint Martin, Haiti, Dominican Republic and St. Croix United States Virgin Islands have only reported sporadic transmission following recent introduction.