Talking at the organization's yearly World Health Assembly, Dr Chan said specialists had "failed" in the 1970s as to understanding malady conveying creepy crawlies.
More than 60 nations and regions now have proceeding with Zika transmission.
Most as of late, the disease, spread by mosquito chomps, achieved Africa.
The infection is thought to bring about genuine birth deformities amid pregnancy and has been announced a worldwide general wellbeing crisis.
As indicated by Dr Chan, flare-ups that get to be crises dependably uncover particular shortcomings in influenced nations and light up the issue lines in our aggregate readiness.
Dr Chan included that Latin America and the Caribbean, which have been hit hard by Zika, have the most astounding extent of unintended pregnancies on the planet.
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