With social distancing guidelines emphasizing maintaining physical space between people, and reading accounts of New York City, it may seem like COVID-19 is more prevalent in areas of high density. This Pennlive article goes so far as to suggest urban residential patterns spread of the virus: “There is no question that people in more densely populated areas are at a greater risk…City dwellers will more often live apartments and row homes when compared to their suburban and rural counterparts.”
So far though the data does not support this intuition. Here is a plot comparing population density with COVID-19 case rates for . Each blue dot represents a PA county. There is not a strong correlation between density and COVID-19 cases. The red data point is Allegheny County.
Confirmed cases is an imperfect measure since there has not been sufficient testing to identify all cases, and the rate of testing varies between different PA counties. Nate Silver at FiveThirtyEight has suggested using the positive test rate as an alternate measure. A county that has a low case count because it has conducted few tests rather than because there are few cases would have a high positive test rate. Using this metric there is no correlation between population density and COVID-19 prevalence.
Therefore, although further evaluation is needed, claims that COVID-19 is more common in densely populated areas should be treated with skepticism.
In several ways, COVID-19 represents a greater health risk to low density PA counties. This Report shows maps of which counties have various risk factors for COVID-19. On average, PA counties with low population densities have:
- a greater percentage of their population of age 60
- a higher rate of cardiovascular hospitalizations
- a higher rate of diabetes
- fewer hospitals and fewer hospital beds per capita
- fewer physicians per capita
Therefore even if the case rate is lower in rural areas (which it doesn’t appear to be), the mortality rate and incidence of severe health implications may end up being higher in rural and low density areas.
Allegheny County in particular is fortunate that we have excellent healthcare infrastructure and capacity, and so far a low incidence of COVID-19 cases.
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