Speaking at a press conference in Rio de Janeiro, Margaret Chan, the director-general of the World Health Organization said that the Zika outbreak would likely worsen before nations besieged by the mosquito-borne virus linked to thousands of birth defects in Brazil see relief.
"Things may get worse before they get better … Don't be surprised to see microcephaly reported in other parts of Brazil ... We are dealing with a tricky virus, full of uncertainties, so we should be prepared for surprises," she said.
Chan gave these comments as she ended her two-day visit to Brazil, which is considered the epicenter of the Zika crisis.
A total of 46 countries have reported some level of evidence of Zika infections and up to 130 countries are home to the Aedis aegypti mosquito that carries the virus, meaning the eventual spread could be enormous.
Much remains unknown about Zika, including whether the virus actually causes microcephaly, a condition marked by unusually small heads that can result in developmental problems. Chan underscored that scientists are still working to determine causality between the virus and the birth defect.
Brazil has confirmed more than 580 cases of microcephaly and considers most of them to be related to Zika infections in the mothers. Brazil is investigating more than 4,100 additional suspected cases of microcephaly.
After Brazil, Colombia has been hardest hit by Zika infections with the country's health officials reporting on Wednesday a probable case of microcephaly possibly linked to Zika in an aborted fetus.