Population density and covid-19 with 50 US states

Many factors including luck play a role in covid-19 spread, including government policy, healthcare readiness, citizen response, demographics, and luck. Different countries are going to be affected differently, and bigger more populous countries have more people 'available' to be infected and killed. Here, I talk about another factor - population density. Higher population density makes it easy for disease to spread more widely. Thus, cities are more strongly affected than suburbs, which are in turn more strongly affected than rural areas.

In addition to dividing the number of confirmed cases (or deaths) by population size, we can look at the epidemic in terms of population density. Below, I show a snapshot of daily cases averaged across last 7 days against population density for the 50 US states. It should be pretty clear that states with higher population density tends to be with more new confirmed cases per million. This should not surprise anyone with basic knowledge of disease spread.

A similar graph is shown above looking at average deaths instead of new cases. This looks similar to the first graph, but there are some noticeable differences. One thing to remember is that death is a lagging indicator of covid-19 disease spread. A spike in new confirmed cases will not show up as death for a week or more. States like Massachusetts, Connecticutt, New York, and Pennsylvania had earlier spike in covid-19 spread as opposed to states like Rhode Island, Maryland, and Delaware. Deaths per million in the latter group of states are expected to catch up to the former group in the near future - provided that factors such as testing are equivalent.

Since many less densely populated states are bunched up together in the lower left corner, I made two more charts for a better view of these states. Here states like Nebraska, South Dakota, and Illinois stick out as having more new cases than average according to the correlation. On the other hand, States like Alaska, Montana, Vermont, West Virginia, South Carolina, North Carolina, and Hawaii have fewer new cases than average according to the correlation.

With an expectation that covid-19 death is a lagging indicator, we may expect South Dakota and Nebraska to have increase in deaths relatively soon - provided that testing, etc. are equivalent. Meanwhile, states like Lousiana and Michigan may see comparatively fewer deaths fairly soon.