WHO Warns Zika Virus 'Likely' to Spread to U.S.

The World Health Organization (WHO) has warned the mosquito-borne Zika virus will likely reach nearly all of North and South America.

The WHO explained in a statement Monday that the virus — which has been linked to birth defects — is set to spread across the Americas because the populations have not been exposed to the virus before. The statement said “Zika virus will continue to spread and will likely reach all countries and territories of the region where Aedes mosquitoes are found” — that includes all of the Americas except Canada and Chile.

Zika has already reached 21 territories and countries in North and South America. As well as causing headaches, fever and conjunctivitis, it has been suspected of contributing to a surge in birth defects that causes babies to be born with uncommonly small heads.

U.S. officials are currently pushing to develop a vaccine for the Zika virus.

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Write to Julia Zorthian at julia.zorthian@time.com.