What COVID, five years later, can teach us in an age of pandemics. From afar, the images look like clusters of tiny, multicolored dots strewn across paper. “But the dots tell a story,” immunologist Gigi Gronvall says about the two prints she framed and hung behind her desk at the Johns Hopkins Center for Health Security.
One image shows the meticulous mapping of a London-based cholera outbreak in 1854 by British physician John Snow, whose work pinpointed the source of the sickness: a contaminated water pump in the Soho district. “The prevailing theory at the time was that cholera spread through air,” Gronvall says of Snow’s groundbreaking work. “But by gathering and mapping the data, Snow uncovered what we know to be true today—cholera spreads through contact with sewage and feces.”
Dots delineate a different infectious disease in the other, more complex image. There, arrows point up and down and sideways to pink, black, and blue circles, squares, and triangles, tracking viral and genetic material gathered in January 2020 from animals and stalls at the Huanan Seafood Wholesale Market in Wuhan, China. A data visualization from a paper in the journal Cell (September 2024), the intricate markings reveal the presence of SARS-CoV-2, the virus that causes COVID-19, in the materials tested.