The World Health Organization said Friday that the growing spread of Zika around the world and basic gaps in knowledge about the virus’s devastating complications in babies continue to make Zika a global health emergency.
After convening its expert committee this week, the U.N. health experts said that more research needs to be focused on what other factors besides the mosquito-borne virus could be causing severe birth defects, such as microcephaly.
One of the most fundamental questions in this current epidemic is why countries such as Brazil, the epicenter of the current epidemic, have reported nearly 2,000 cases of microcephaly and other brain abnormalities, while countries such as Colombia, where more than 18,000 pregnant women have been infected since last fall, have reported fewer than three dozen cases.
Scientists need to examine possible factors that could affect Zika’s damage, including genetic factors, environmental contaminants, and other co-infections, said David Heymann, the committee’s chair and an infectious disease professor at the London School of Hygiene and Tropical Medicine.
“A whole range of co-factors must be eliminated to say, with certainty,” that the only culprit is the Zika virus, he said.
Peter Salama, WHO’s executive director for outbreaks and health emergencies, said researchers need to understand whether the time lag between when an outbreak occurs to when birth defects show up nine months later could account for country-by-country differences, or whether it is “truly something to do with co-factors.”
Meanwhile, the virus continues to infect new countries, including most recently Singapore, which reported 189 confirmed cases Friday.
“An extraordinary event is becoming, unfortunately, an ordinary event,” Heymann said.
WHO officials also said Brazil reported no confirmed cases of Zika following the Rio de Janeiro Olympics. That data is based on information collected by authorities on people who sought treatment at health facilities who were athletes or spectators.
Most people with Zika don’t have symptoms, but Salama said enhanced surveillance by WHO of the Olympic delegations shows no large-scale transmission of Zika, confirming the earlier assessments of WHO and the Centers for Disease Control and Prevention that the Olympics posed no significant additional risk of spreading Zika.
A study published Thursday identified eight countries in Asia and Africa that researchers say are at the greatest risk of Zika virus transmission.
The countries — India, China, the Philippines, Indonesia, Nigeria, Vietnam, Pakistan and Bangladesh — all have hot and humid climate conditions; the type of mosquitoes that primarily spread the virus; a high volume of travelers returning from Zika-affected areas in the Americas; and large, dense populations. And several have limited health-care resources.
