The Zika virus spreading across Central and South America constitutes a "public health emergency of international concern," the World Health Organization declared on Monday.
The virus has been linked to a sharp increase in birth defects, including a particularly devastating condition known as microcephaly.
An emergency committee of 18 experts established by the WHO took the step of sounding the alarm on Zika after an all-day meeting in Geneva on Monday. The designation will help free up resources and marshall world governments to prioritize research and other actions to fight the illness.
In addition to birth abnormalities, the Zika virus has also been tied to an uptick in adult neurological disorders such as Guillain-Barré syndrome, which can cause paralysis.
Zika alone would not be a public health emergency, said David L. Heymann, the chair of the emergency committee, since the symptoms of the virus itself tend to be mild. It’s the association with microcephaly and neurological disorders that caused the declaration to be made.
The Zika virus is not new, having been discovered in the Zika Forest of Uganda in 1947. Until late 2015, most outbreaks of the illness had been mild.
However, since October 2015, an expanding outbreak of Zika has spread across Brazil, possibly aided by El Niño-related heavy rains and flooding, active virus transmission is now occurring in about two-dozen countries and territories from Brazil to the Caribbean.
The spread of the illness is aided by the broad distribution of the mosquito that spreads it as well as the lack of immunity among populations in the Western Hemisphere. Zika cannot be spread person-to-person and is not airborne, though much is unknown about whether it can be contracted sexually.
Zika cannot be spread person-to-person and is not airborne
The virus is spread by the Aedes aegypti mosquito, which also carries dengue and the chikungunya virus. Because the mosquito is widespread across a vast stretch of the western hemisphere, from South America to the U.S. border with Canada, it is possible that travelers and international trade will spread the virus into the U.S.
The Centers for Disease Control and Prevention (CDC) has stated that they expect cases of active Zika virus transmission to occur in the U.S., most likely in the Southeast, but that these outbreaks are likely to remain relatively small.
The CDC has issued travel advisories to more than 20 countries and territories where there is active Zika virus transmission taking place, warning pregnant women not to travel there due to the risk of microcephaly.
Researchers are racing to determine how the virus is being transmitted from a pregnant women to the fetus, as well as to unravel the mystery surrounding neurological disorders in adults that contract Zika infections.
Margaret Chan, the director-general of the WHO, said the link between Zika virus infection and microcephaly as well as neurological disorders “is strongly suspected though not yet scientifically proven.” The suspicions were enough for the emergency committee to act, she said.
“The evidence is growing and it’s getting strong,” Chan said regarding the link between Zika infections and the debilitating, and in some cases deadly, outcomes.
“There is urgent need to do a lot more work,” Chan said.
In addition to coordinated research efforts, Chan said the WHO is advising countries to undertake measures to fight mosquitoes, and said there is no basis for travel bans or restrictions meant to prevent the spread of the illness.
The Zika virus itself typically causes only mild symptoms, lasting from several days to a week, according to the CDC. The most common symptoms are fever, rash, joint pain and conjunctivitis (red eyes). Only about one in five people infected with the virus actually show symptoms.
The Zika outbreak constitutes a test of the reforms the WHO put in place in the wake of the Ebola outbreak in West Africa. During that event, which only recently concluded, the cash-strapped international agency was accused of moving far too slowly in responding to urgent pleas from the ground in impoverished West African nations.
On Jan. 27, Brazil’s health ministry stated that reported microcephaly cases since October of 2015 have reached 4,180, an increase from the week before, and a tremendous surge compared to previous figures. Before the Zika virus outbreak, microcephaly was extremely rare in Brazil, with only about 150 reported cases per year.
During a press conference call on Jan. 28, Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health in Maryland, said the U.S. is already stepping up research efforts to develop, test and deploy a Zika vaccine. However, he said it is unlikely that such a vaccine would be available for a couple of years.
He said the virus is "the latest in a series of mosquito-borne diseases that have expanded their range in the past 20 years or so."
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