More than a million people die each year from severe diarrhea caused by contaminated water, according to the Global Burden of Disease Study 2016. Viruses are often to blame: in fact, rotavirus is the leading cause of these deaths. But it’s been challenging to find effective, inexpensive, and practical ways to remove these minuscule pathogens from drinking water in the developing world, where waterborne disease is most prevalent.
Enter Moringa oleifera, a tropical tree whose seeds have long been used by indigenous people to purify water. Last year, Manish Kumar of the University of Texas at Austin, Stephanie Velegol of the Pennsylvania State University, and their colleagues introduced a prototype water filter made with a column of sand coated with an extract from Moringa seeds. Though it effectively stripped bacteria from water, “we knew we wouldn’t be able to have worldwide impact unless we could also remove viruses,” Velegol says. Now the researchers show that the system eliminates 99.99999% of MS2 bacteriophage, a well-studied virus similar to rotavirus, from water—a viral reduction surpassing the 99.99% required by the US Environmental Protection Agency for drinking water (Environ. Sci. Technol. 2019, DOI: 10.1021/acs.est.9b03734).
The researchers find that the system grabs the virus so efficiently because a protein in Moringa seeds called MoCBP binds to a protein on the capsid, or shell, of the virus. Molecular docking simulations predict a similar response with rotavirus. The team is now working to refine and scale up the filtration system.