Jeffrey E. Harris*  - Department of Economics - Massachusetts Institute of Technology

Abstract. New York City’s multi-tentacled subway system was a major disseminator – if not the
principal transmission vehicle – of coronavirus infection during the initial takeoff of the massive
epidemic that became evident throughout the city during March 2020. The near shutoff of
subway ridership in Manhattan – down by over 90 percent at the end of March – correlates
strongly with the substantial increase in the doubling time of new cases in this borough. Maps of
subway station turnstile entries, superimposed upon zip code-level maps of reported coronavirus
incidence, are strongly consistent with subway-facilitated disease propagation. Local train lines
appear to have a higher propensity to transmit infection than express lines. Reciprocal seeding of
infection appears to be the best explanation for the emergence of a single hotspot in Midtown
West in Manhattan. Bus hubs may have served as secondary transmission routes out to the
periphery of the city.