Zika virus
US Health officials are investigating 14 new cases of Zika virus possibly transmitted by sexReuters

The World Health Organisation (WHO) has warned that there could be nearly four million cases of Zika virus infection, stating that it was spreading "explosively".

WHO has called for an emergency meeting on 1 February to decide if the outbreak of the mosquito-borne disease should be declared an international health emergency. 

The Zika virus is believed to be linked to birth defects in babies, who are born with abnormally small heads due to stunted brain growth. 

While there has been no proof to link the virus to the birth defect called microcephaly, WHO Director-General Dr Margaret Chan said on Thursday: "The level of alarm is extremely high." 

"A causal relationship between Zika virus infection and birth defects and neurological syndromes has not been established, but is strongly suspected," WHO said. 

The Zika virus outbreak that began in Brazil in recent months has spread to at least 23 countries in Latin America and the Caribbean. 

In Brazil, as many as 4,000 babies have been born with birth defects due to microcephaly after the first case of Zika virus infection was reported in the country last May. 

Currently, 1.5 million people are estimated to have been affected by the Zika virus.

The virus is spread by the Aedes mosquito that also spreads dengue and chikungunya.

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