- London Tube: Analysing the link between public transport use and airborne transmission: mobility and contagion in the London underground
“Higher rates [of influenza-like cases] can be observed in boroughs served by a small number of underground lines: passengers starting their journey in these boroughs usually have to change lines once or more in crowded junctions such as King’s Cross in order to reach their final destination.” “On the other hand, lower influenza-like rates are found in boroughs where either the population do not use public transport as the main form of transport to commute to work; or boroughs served by more underground lines, which guarantee faster trips with less stops and contacts with fewer people.”
Impact on riders:
The first is that the rate of disease transmission is related to the number of trips and average number of stations per trip along the entire subway line, and not just to the number of entries at any one subway station. Second, passengers entering the subway line even at a remote, less populous station are slowing down the system, thus increasing the transit time that the S’s stay in contact with the I’s. Third, those uninfected S- passengers who cram shoulder-to-shoulder into a particular subway are increasing train-car density and thus raising the average number of other S-passengers infected by an I-passenger who happens to be standing in the middle of the train. Fourth, local trains – like the Flushing local – are more likely to seed epidemic infections than express lines. Finally, an entire subway line, rather than the individual stations or subway cars, is the appropriate unit of analysis.
Impact on subway workers:
3D video of a cough and its duration in a grocery store. Download JPods Paper pdf
By April 16, the MTA had reported 68 deaths among more than 2,400 subway and bus employees who had tested positive. “Another 4,400 are on home quarantine and thousands more are calling out sick.”
“Data from TWU Local 100 (subway workers) indicate… more than three times the rate… the most affected hotspot.”
It is hard to imagine any plausible explanation for these workers’ losses except that their place of work was the principal source of their coronavirus infections. How ironic it is that unfathomable tragedy of these frontline workers turns out to be the clincher that transports us from correlation to causation.