Despite reports to the contrary over the past few weeks, recent studies suggest the link between the Zika virus and microcephaly is stronger than previously believed. In another new development, the World Health Organization announced the sexual transmission of Zika virus happens with more frequency than was first imagined.
Both developments led WHO on Tuesday to strongly caution pregnant women against traveling to countries experiencing Zika virus outbreaks. The virus appears to be spreading rapidly, with the CDC reporting at least 153 cases in the United States as of March 2, ostensibly by those who had traveled to countries with outbreaks.
On Friday, researchers announced they had discovered the possible mechanism by which Zika virus can cause microcephaly — a rare birth defect that causes babies to be born with abnormally small heads and underdeveloped brains.
“Working with lab-grown human stem cells, scientists found that the virus selectively infected cells forming the brain’s cortex, the thin outer layer of folded gray matter,” the Washington Post reported. “Its assault made those cells more likely to die and less likely to divide normally and make new brain cells.”
Hengli Tang, a researcher with the University of Florida and one of the study’s authors, told reporters during a conference call, “What we show is the first piece of evidence” marking the hypothetical link between Zika virus and microcephaly. “We’re literally the first people in the world to know this, to know that this virus can infect these very important cells and interfere with their function.” Though the study didn’t discern whether the virus is capable of reaching the brain, it did show that if that is possible, “this virus can do a lot of damage.”
The findings by researchers from Johns Hopkins University, Emory University, and Florida State University show the clearest evidence for how the Zika virus harms fetuses. As scientists and researchers rush to verify that link, others have reported theories contending microcephaly was caused by everything from vaccines to fungicides. But microcephaly’s connection to the virus is strengthening, as researchers have also documented the presence of the Zika virus in the brains of newborns who died, as well as in the placental fluid of infected mothers. Though the findings aren’t considered definitive proof of Zika virus’ role in causing microcephaly, scientists believe it certainly adds to the hypothesis.
WHO Director-General Dr. Margaret Chan said, “reports and investigations in several countries strongly suggest that sexual transmission of the virus is more common than previously assumed.” Her statement came after an emergency committee meeting on Tuesday, which also noted the Zika virus’ link to microcephaly and other birth defects.
In fact, WHO reported that nine countries have also announced increasing cases of Guillain-Barré syndrome — a condition causing paralysis or even death — in children, teenagers, and adults, which is also strongly believed to be linked to Zika virus. A study published in the Lancet on February 29 described a nearly certain link between Guillain-Barré and the Zika virus. According to the study authors:
“This is the first study providing evidence for Zika virus infection causing Guillain-Barré syndrome. Because Zika virus is spreading rapidly across the Americas, at risk countries need to prepare for adequate intensive care beds capacity to manage patients with Guillain-Barré syndrome.”
ABC News reported there are now over a dozen cases being investigated in the U.S. in which Zika virus may have been sexually transmitted. Widespread outbreak of the virus throughout both American continents led WHO to declare it constitutes a global emergency.
Zika virus remains largely mysterious to scientists, who theorize its incubation period lasts approximately one week — meaning travelers account for the large number of cases reported in areas not experiencing outbreaks. Findings the virus may be transmitted through sex more often than previously realized fuels concern about its spread around the globe.
Another cause for concern surrounds the lack of symptoms in nearly 80 percent of those who contract Zika virus. Symptoms in those who have them mimic those of dengue fever — which is also transmitted by the same species of mosquito, Aedes aegypti — and can include fever, rashes, headaches, fatigue, and muscle and joint pain. Though Aedes mosquitoes normally populate Florida, the Gulf Coast, and Hawaii in the U.S., as the Observer noted, hot summer weather has been known to drive them as far north as Washington, D.C. With February reported to be the hottest in recorded history, it wouldn’t be unlikely to imagine such an expansion of the Aedes population this year.
WHO now recommends pregnant women refrain from travel to areas of ongoing outbreak, and said they should practice safe sex or abstinence for the duration of their pregnancies if they have partners who have traveled to such areas.