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Purple areas highlight countries and territories now reporting Zika virus transmission.

Purple areas highlight countries and territories now reporting Zika virus transmission.

Centers for Disease Control and Prevention

Worries about brain damage in infants linked to Zika leads WHO to declare a public health emergency

Increasingly strong links between the spread of Zika virus and microcephaly in newborns led the World Health Organization (WHO) today to declare a Public Health Emergency of International Concern.

WHO Director-General Margaret Chan in Geneva, Switzerland, made this declaration upon the advice of a committee of 18 experts and advisers, who she said “agree that a causal relationship between the Zika infection during pregnancy and microcephaly is strongly suspected though not yet scientifically proven.” Zika, a mosquito-borne virus, is currently spreading through 24 countries in Latin America and the Caribbean, plus Cape Verde, an island off West Africa. Chan noted that there was “a particularly strong association in time and in space” between the arrival of the virus and the detection of microcephaly and other neurological disorders. Although Brazil has had more than 4000 suspected cases of microcephaly, it has confirmed only 270 cases of this brain-damaging condition in children born to mothers who had evidence of having been infected with the virus.

Although Brazil is the only country to report a spike in microcephaly during the current outbreak, French Polynesia in 2014 saw a rise in this rare disorder concurrent with viral spread, Chan said. Brazil, El Salvador, and French Polynesia also suspect Zika virus may have led to increased cases of a neurological disorder in adults called Guillain-Barre syndrome that causes temporary paralysis. “The committee advised that the cluster of microcephaly and other neurological complications constitute an extraordinary event and public threat to other parts of world,” Chan explained. She was careful to note that her declaration of concern focused on these clusters and not the spread of the virus itself, which causes no symptoms in 80% of people it infects, and a short-lived rash and fever in the other 20%.

Many criticized WHO for not sounding this alarm when the Ebola outbreak surfaced in 2014. “It was a very difficult decision to discern between what is a Public Health Emergency of International Concern and what should be precautionary measures because of a possible relation between Zika and these clusters,” explained the chair of the committee, epidemiologist David Heymann of the London School of Hygiene & Tropical Medicine.

Chan suggested that pregnant women not living in Zika-affected countries may want to delay travel to those areas but did not issue a formal travel alert for them, as the U.S. Centers for Disease Control and Prevention has done. Chan stressed that “the committee found no public health justification for restrictions on travel or trade to prevent the spread of Zika virus.” Many countries ignored similar recommendations during the Ebola epidemic in West Africa and imposed what WHO saw as unnecessary and even counterproductive travel and trade restrictions.

In tandem with the declaration, the committee made two major recommendations: Standardize surveillance for microcephaly and other neurological disorders in places where Zika is spreading, and intensify research to discern whether the clusters of cases are truly linked to the virus.

“There is an urgent need to do a lot more work,” Chan said. She also stressed that the world had to step up mosquito control efforts, surveillance of Zika, and efforts to develop a vaccine. “Can you imagine if we do not do all this work now and wait until the scientific evidence comes out?” she asked.

Lawrence Gostin, a lawyer who specializes in global health law at Georgetown University in Washington, D.C., supports  the declaration but stated in a press release that WHO needs to spell out more explicitly how it intends to respond. “Margaret Chan was silent on what strategy the organization will take on the ground to control Zika and how she will mobilize the major funding needed for surveillance, mosquito control, and critical research,” Gostin contended. “Without a clear strategy and ample resources, sounding an alert is simply not enough.”