Since the major mode of transmission of the coronavirus is between people who are in proximity to each other, it seems intuitive that in societies where there are more crowded living conditions there would be more spread of Covid-19. Since the first days of the pandemic, people have suggested that the virus was spreading more rapidly in areas and countries that were more densely populated.
However this article, in a widely read usually responsible newspaper, argues that the relationship between population density and the spread of Covid-19 is a “myth” and has been “debunked”.
Stop Blaming COVID-19 Deaths On Population Density
While there are quite a number of good arguments here, this is a classic case of someone forming his own conjecture without reading the science. I don’t think the reporter who wrote this article reviewed any of the many scientific studies that examined this question. This is a really good example of people who “do my own research” instead of studying the actual science. This lazy approach has been a big reason there has been so much misinformation circulated about the pandemic. It’s not easy to read some of the science. Published papers are long and dense with a lot of detail and you need to have some understanding of statistics to understand the research and the results. Read this for example.
Temperature and population density influence SARS-CoV-2 transmission
The Huffpost reporter argues quite well that there are many reasons to explain the spread of Covid, such as
– public health policy
– residential overcrowding (which is not the same as population density)
– work environments which increase the frequency of face-to-face interactions
But this does not mean that population density is not an important factor. There are many factors that affect the spread of a respiratory illness.
It does seem true that there does not seem to be a connection between Covid and population density at the country level. If Covid increased with population density, the data points on this chart. would form a line rising from left to right.
https://ourworldindata.org/grapher/covid-19-death-rate-vs-population-density?yScale=linear&minPopulationFilter=1000000
But when you look at a more granular level, at smaller regions within a country, there does seem to be a very strong relationship. There have been a number of statistical studies to try and analyze this more completely. One of the better papers concludes that
Population density and temperature are drivers of R0 at state level in the United States (p<0.001), but the effect of lockdown is greater.
See Table 1 in Temperature and population density influence SARS-CoV-2 transmission
The additional conclusion about temperature is that as temperature increases Covid cases decrease. This has been widely noted by epidemiologists who have pointed out that in winter, people congregate indoors more than in summer and this is an important factor that gives rise to the spread of all respiratory illnesses such as seasonal flu.
It’s pretty easy to see that population density drives Covid cases yourself. Charts on the next few pages show it for the U.S. and Europe. If you look at the Covid hot spots on the first map, it is usually an area of high population density on the second map.
U.S. Covid hot spots Jan 4, 2022
https://www.nytimes.com/interactive/2021/us/covid-cases.html
Europe Covid hot spots Nov 24, 2021
https://www.nytimes.com/interactive/2021/11/30/world/europe/europe-covid-surge-omicron.html
https://www.eea.europa.eu/data-and-maps/figures/population-density-1992
