What We Know (and Don’t Know) About Zika

Yesterday, the World Health Organization declared Zika to be a global health emergency, the first such declaration since the Ebola outbreak in 2014. The mosquito-borne virus has spread to more than 20 countries in South America and the Caribbean since it was first reported in the Western Hemisphere last year, and may be linked to severe birth defects and, in rare instances, a neurological disorder.

“Although not yet confirmed, the potential link between the Zika virus and birth defects is cause for concern,” says Ian Lipkin, director of the Center for Infection and Immunity. “There have been reports of thousands of babies born with microcephaly, or unusually small heads and brains, and we may find other serious health outcomes associated with the rapid spread of this virus. The efforts of public health officials and researchers will be integral to international efforts to monitor the disease’s spread, develop vaccines, and implement other mitigation strategies.”

The U.S. Centers for Disease Control and Prevention recommends that pregnant women avoid travel to Zika-affected countries. If a pregnant woman who was recently in one of these areas becomes sick, she should see her doctor.

“There is a test for active infection which uses a molecular method to determine if the virus is in the blood,” says Stephen S. Morse, professor of Epidemiology. “If someone has had the infection and recovered, then you test for antibodies. These tests are not normal commercial tests, though. They have to be done by health departments.”

Yesterday, Morse answered more than 30 questions about Zika on the popular website Reddit. The question that garnered greatest audience interest was whether a woman who got pregnant long after being infected with Zika would still be at risk for birth defects. Morse said there would likely no longer be a risk, but cautioned that there is insufficient data to know for sure. In fact, many aspects of the Zika outbreak remain unknown.

Scientists have also yet to determine the frequency of serious Zika-related outcomes, including microcephaly, when a child is born with an abnormally small head and brain, and Guillain-Barré Syndrome, which harms the peripheral nervous system. Also unknown is how many mosquito species are capable of carrying the virus and the extent to which Zika is capable of being transmitted through intercourse and blood transfusion.

There have already been a number of cases of people traveling to affected areas who contracted Zika and entered the United States. Transmission in this country is technically possible in areas of the Gulf Coast with Aedes Aegypti, the mosquito species known to carry the virus. Though climate warming might expand its habitat in the coming years, experts believe Zika is unlikely to gain a foothold in the U.S. due to more limited contact between people and mosquitoes.

“Many Americans go from their air-conditioned home to their air-conditioned car, to their air-conditioned workplace,” says Jeffrey Shaman, associate professor of Environmental Health Sciences. “They’re very segregated from mosquito populations. In the rare occasions that they see them, they swat them.”

In countries where Zika is now endemic, efforts to control its spread include spraying for mosquitos inside homes and draining standing water. “Impoverished populations who cannot afford screens, air conditioning, and insecticides are at greater risk,” says Rachel Moresky, director of sidHARTe and the International Emergency Medicine Fellowship program, and assistant professor of Population and Family Health and Medicine.

Moresky is one of four Columbia authors of a new article in the British Medical Journal that draws on lessons from global health crises like Ebola to outline six proposals to reform the World Health Organization’s capabilities to respond to current and future challenges.

Ian Lipkin said he and his team are currently working to address the Zika outbreak on two fronts. First, they are developing tests to allow them to quickly determine whether someone is infected by Zika or other mosquito-borne viruses like Dengue, Chikungunya, or West Nile. Second, they are working to understand the connections between infection and outcomes like microcephaly.

“By understanding how the viruses cause disease we have the potential to intervene,” says Lipkin. “Many of our colleagues are beginning to work on trying to develop vaccines to prevent infection with Zika virus, as well as drugs that they can use to suppress the rate of growth of the virus when someone becomes infected.”