If social distancing keeps people safe from coronavirus, why are crowded, densely populated locations associated with lower coronavirus death rates?
Crowded city streets, subways, and buses have been considered the most likely places to become infected with COVID-19 over the past few months. Surprisingly, however, a new study from the Johns Hopkins Bloomberg School of Public Health concludes that densely populated spaces aren’t actually linked to higher infection rates.
Even more confounding, the study’s analysis indicates that crowded, dense locations are associated with lower coronavirus death rates.
In all, COVID-19 infection and death rates were assessed across 913 U.S. metropolitan counties. After researchers accounted for additional factors like race and education, the population density within each county was not significantly linked to infection rates. As mentioned, denser counties, as opposed to more rural, sprawling areas with smaller populations, were associated with lower death rates. The study’s authors speculate this is because denser, urban areas often offer better healthcare services.
Instead, higher coronavirus infection and death rates seem to be linked to a metropolitan area’s size, not its density. So, cities that are very big and stretch across multiple counties that are “tightly linked together through economic, social, and commuting relationships” appear to be most at risk of high coronavirus infection rates.
After accounting for a variety of factors (metro size, age, race, education), the study concludes that doubling the activity density of a given area would result in a 11.3% reduction in coronavirus deaths. How is this possible? Researchers theorize it’s because of faster, more widespread adoption of social distancing in urban areas, as well as superior medical services.
As unbelievable as some of these findings sound, the research team say they’ve continued to update their projections as the pandemic has progressed over time, and all of the data continues to validate their conclusions.
The researchers’ theory that crowded, densely populated areas have lower death rates because people there are somehow better at socially distancing from other people is silly.
Here’s what’s likely happening: social distancing and the lockdown are preventing populations from developing herd immunity by preventing the most valuable immunity-generating assets (kids, teenagers, and young adults) from getting infected quickly and gaining immunity. Consequently, interactions with people become increasingly more likely to result in someone spreading the virus because most people interacting with other people are adults.
Higher population density offsets the effects of the lockdown, because staying away from people is harder the more crowded the area. This means that the virus spreads faster and becomes weakened through the effects of herd immunity, resulting in a lower death rate over time.
The idea that the lockdown and social distancing prevent the development of herd immunity is supported by the J.P. Morgan study that showed that, in most places, infection rates decreased after the lockdown was lifted.