An outbreak of birth defects and neurologic disorders linked to the Zika virus meets the criteria for a global health emergency, the World Health Organization said Monday.
WHO director-general Dr. Margaret Chan made the declaration following an emergency committee meeting held earlier in the day.
This is only the fourth time since 2009 that the UN health agency has declared a “public health emergency of international concern” under the International Health Regulations, with previous declarations made for H1N1, polio, and Ebola.
“After a review of the evidence, the committee advised that the clusters of microcephaly and other neurological complications constitute an extraordinary event and a public health threat to other parts of the world,” said Chan, who accepted the recommendations of an expert panel.
“In their view, a co-ordinated international response is needed to minimize the threat in affected countries and reduce the risk of further international spread.”
Dr. David Heymann, the chair of the committee, clarified that the emergency is not being called over Zika specifically, but the cluster of neurologic disorders currently being linked to the virus, which lacks a vaccine or effective treatment.
Zika was first discovered in Uganda in 1947. For decades it was believed to only cause mild disease, including fever, joint pain and rash, and experts estimate only 80 per cent of people show symptoms.
The virus is spread by a day-biting mosquito called the Aedes aegypti, which can be found in every country in the Americas except Canada and continental Chile.
After emerging in Brazil last spring, Zika has been spreading explosively across the Americas — at least 24 countries and territories have now reported locally acquired infections — and raising new concerns over serious neurological side effects.
In Brazil, the country hardest hit by Zika virus, health officials are reporting an alarming surge in microcephaly, a condition associated with abnormally small heads and brains in newborn babies. A number of countries are also reporting increases in Guillain-Barré syndrome, a potentially fatal autoimmune disorder that can cause temporary paralysis.
Experts caution that a causal link between Zika and microcephaly or Guillain-Barré has not yet been proven and some question whether the reported increase is simply the result of heightened awareness; perhaps Brazilian doctors are finding more cases because they are now searching for them so intensely.
Microcephaly can also be tricky to diagnose and while Brazilian health authorities are investigating more than 4,100 reported cases, they have only confirmed 270 far, discarding 462 as false diagnoses.
But the numbers represent an undeniable increase in Brazil, which previously reported fewer than 150 cases of microcephaly per year. The WHO has said that a causal relationship between Zika and microcephaly is “strongly suspected.” Scientists with the U.S. Centers for Disease Control and Prevention have isolated the virus from the brains of two Brazilian babies, both of whom had microcephaly and died shortly after birth.
A Zika outbreak in French Polynesia in 2013 and 2014 was also associated with an increase in both microcephaly and Guillain-Barré syndrome.
The WHO said many studies are now underway to investigate the causal link, with several others soon to be launched.
The WHO has said that between three and four million people could be infected over the next 12 months, though this is a rough estimate based on data from past outbreaks of dengue, a virus related to Zika.
A number of countries affected by the Zika virus are now urging women to delay their pregnancies, with El Salvador even advising that women wait for two years. Other countries, including Canada and the United States, have issued travel advisories, recommending that pregnant women — and those planning to become pregnant — avoid Zika-affected areas.
The WHO emergency committee’s conclusion on Monday, however, is that there are currently “no public health justifications” for restrictions on travel or trade.
“The real difficulty is balancing the risk of further international spread with the needs of those countries experiencing the worst of the current outbreak,” Jonathan Ball, a professor of molecular virology with the University of Nottingham, said in a written statement shortly after the WHO’s announcement.
“A kneejerk response would be to ban travel and trade with countries affected, but the truth is that the potential problem is much wider. It wouldn’t really be feasible to lock down the affected countries to try and stop the spread of a virus that is carried by the Aedes mosquito, especially when affected and unaffected countries border one another.”
Urgent efforts to produce a vaccine for Zika are now underway. Laval University’s Dr. Gary Kobinger — who helped develop a successful trial vaccine for Ebola with the Public Health Agency of Canada — has said that his team is working on a vaccine that could be available for emergency use by the end of the year.
Most experts warn, however, that a Zika vaccine is still at least three or four years away.