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Geneva: The World Health Organisation has declared the mosquito-borne Zika virus to be an international public health emergency, as the disease linked to thousands of birth defects in Brazil spreads rapidly.
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WHO Director-General Margaret Chan said on Monday an international co-ordinated response was needed, although restrictions on travel or trade were not necessary.
The emergency designation was recommended by a committee of independent experts to the United Nations agency following criticism of a hesitant response so far. The move should help fast-track international action and research priorities.
The WHO said last week the Zika virus was "spreading explosively" and could infect as many as 4 million people in the Americas.
The agency was criticised for reacting too slowly to the Ebola epidemic in west Africa that killed more than 10,000 people, and has promised to do better in future global health crises.
The WHO's International Health Regulations emergency committee brings together experts in epidemiology, public health and infectious diseases from the Americas, Europe, Asia and Africa.
Brazil has reported nearly 4000 suspected cases of microcephaly, in which infants are born with smaller-than-usual brains. The health ministry has linked the condition to Zika, although the connection is not yet definitive.
Brazilian Health Minister Marcelo Castro said the epidemic was worse than believed because in 80 per cent of the cases the infected people had no symptoms.
As the virus spreads from Brazil, other countries in the Americas are also likely to see cases of babies with Zika-linked birth defects, experts believe.
The Pan American Health Organisation said Zika had spread in 24 nations and territories in the Americas.
Meanwhile, the US Centres for Disease Control and Prevention on Monday added four more countries and territories to a growing list of places where travellers risk being infected with the rapidly spreading virus.
The CDC added American Samoa, Costa Rica, Curacao, and Nicaragua to a list of 28 other regions.