WHO chief Margaret Chan said Tuesday that the U.N. health agency still is waiting for its members to provide another $4 million to deal with the growing threat from the Zika virus. "The more we know, the worse things look," Chan told reporters at WHO headquarters in Geneva. "In less than a year the status of Zika has changed from a mild medical curiosity to a disease with severe public health implications." Zika has been linked to thousands of suspected cases of microcephaly, a rare birth defect, in Brazil, and a neurological disorder called Guillain-Barre Syndrome. The WHO and its American arm PAHO have asked for $25 million to fight Zika and have received $3 million, and now are in an "active discussion" over the next $4 million, said Chan, who called the funding shortfall "pretty serious."