International researchers have compiled an atlas of microorganisms residing in subways (or mass transit) in major urban centres. Building on enthusiasm for geneticist Christopher Mason’s 2015 research on microbes in New York City’s subway system, this study dispatched teams of scientists and volunteers to swab turnstiles, railings, ticket kiosks, and benches inside transit stations and subway cars in 60 cities. Their findings, published in Cell, include the discovery of 10,000 previously unidentified species of viruses and bacteria.