The push notifications came vibrating in this afternoon: “The Zika virus is a global emergency,” the one from The New York Times said. “World Health Organization declares Zika to be global public-health emergency,” read The Wall Street Journal’s.
But the declaration — of a “public health emergency of international concern” — wasn’t exactly for Zika, a virus spread by mosquitos that recently came to the Americas and has spread at an alarming rate. The emergency declaration was for a cluster of birth and neurological defects, including microcephaly, that may be connected to the Zika virus.
It may seem a small distinction, but it’s an important one. As David Heymann, chair of an emergency committee gathered to advise the WHO on the declaration, said in a news conference Monday, Zika itself “is not a clinically serious infection.” The virus was first discovered in Uganda in 1947, but cases of the disease were only rarely found in humans until 2007, when an outbreak on an island in Micronesia became the first of several. But until two years ago, it only caused symptoms in approximately 20 percent of people infected, and those symptoms were relatively mild, consisting of flu-like aches and pains, minor rashes or pink eye. Zika has generally been of less concern than several other viruses transmitted by the same mosquito as Zika, namely dengue, chikungunya and yellow fever, which are all endemic in many parts of the world and have never been given the international emergency declaration that these Zika-linked conditions received Monday.
But in 2015, Brazilian officials alerted the world that there had been a surge in babies born with abnormally small heads, a condition known as microcephaly. There have also been reports of an increase in Guillain-Barré syndrome, a disorder where the immune system attacks the nervous system after an infection, often causing temporary paralysis. WHO Director-General Margaret Chan said today that there is strong and growing evidence that these conditions are linked to Zika, which showed up in the same parts of Brazil during the same time period as the increase in reported cases of microcephaly.
But the connections are still very tentative. Of the 4,180 suspected cases of microcephaly, only 270 have been confirmed (462 have been rejected), and only six of those are confirmed to be related to Zika, according to Brazil’s most recent bulletin on the situation. Testing for Zika is complicated (there is no rapid test, and the virus may not stay in the body long enough to be detected in many of the cases), so it may be that more of those cases of microcephaly had Zika than can be confirmed. But some experts have questioned whether there has been an increase in microcephaly and GBS, or just an increase in detection. Several in-depth studies are currently underway in Brazil to establish whether there is in fact a link.
Meanwhile, the emergency declaration is largely a political one — it opens resources for a coordinated international response, which the WHO says will largely focus on research and controlling the mosquito population. Still, the World Health Organization maintains there is no reason to restrict travel or trade.1 They do recommend that in absence of a better understanding of the disease, people should aggressively avoid getting Zika by protecting themselves from mosquitoes.
But as Bruce Aylward, the interim executive director for Outbreaks and Health Emergencies at the WHO, has pointed out, that’s always the case, especially for pregnant women. Zika is new, but the threat of infectious diseases is not.