‘Pandemics balloon in poor neighbourhoods’ is a long-standing dogma in epidemiology. People living in crowded, tightly packed environments, working in conditions that make physical distancing difficult, and not being able to afford precautionary equipment make ideal breeding ground for viruses. Many studies have shown that since people of higher social status have more opportunities to insulate themselves from the virus, infections spread faster in people of lower social status. However, some studies have found that infections spread at the same rate in all strata of society, or even the opposite – that it spreads faster in people of higher social status (Berkessel et al., 2021).
A recent paper by Jana Berkessel et al. provides a new model for the spread of infections that may explain these seemingly contradictory findings. They report two studies that measured the rate of spread of COVID-19 and the Spanish Flu. The first study looked at how the rate of spread of infections varied with social status (regional medium income) at various phases of the current pandemic in 3 countries – the United States, England, and Germany.
Researchers found that in all 3 countries, SARS-CoV-2 spread faster in higher income regions (where people of higher social status live) than lower income regions during the initial phase. Researchers think this had to do with people of higher social status having higher “spatial and relational mobility”. In other words, people of higher social status meet and interact with a more diverse set of persons than people of lower social status. More diverse social contacts mean increased susceptibility to the virus at the early stages of the pandemic. 30 days into the pandemic, higher income regions in the US were hit 9.9 times as hard as lower income regions, 2.8 times harder in Germany, and 1.2 times harder in England.
“People of higher social status exhibit more independent behavior, are more mobile, and possess more diverse social networks; people of lower social status exhibit more interdependent behavior, are less mobile, and possess more homogenous social networks”
By contrast, during the later stages of the pandemic, they found that infections spread faster in lower income regions within the United States and England. In these countries, this reversal in the spread of infections was seen as early as 2-3 months into the pandemic. The reversal was particularly strong in the United States. Researchers found that after 5 months into the pandemic, lower income regions were hit 1.65 times as hard as higher income regions in the US.
Interestingly, in Germany, lower income regions were not hit harder than higher income regions even in the later stages of the pandemic. Researchers think that by having a more egalitarian society and medical system, the country reduced the vulnerability of its lower income population to the pandemic. They also cite the fact that Germany was more successful at containing the pandemic (compared to the United States and England) as a possible reason for the discrepancy.
The second study looked at how the Spanish Flu of 1918 spread in people of lower versus higher social status. It used data from an online collection of memorials (findagrave.com). Researchers took a random sample of 5 million memorials (containing information like name, year of birth, year of death, and burial site) from this online gravesite collection.
Researchers used the first names of the deceased to classify them into lower or higher social status. To support the classification they cite research showing a well-documented trend among parents of higher social status at the time to choose more common first names for their kids (Clark et al., 2015; Lieberson & Bell, 1992; Oliver et al., 2016; Willis & Willis, 1982). They used census data to calculate the probability that a person is of Black race [“it is well-documented that people of Black race were (and still are) among the most socially deprivileged groups in the United States”].
“As such, persons with uncommon first names and a high probability of being Black (e.g., Myrtle Smokes or Avery Tasby) were classified as lower social status than people with common first names and a low probability of being Black (e.g., Amanda Cornett or Michael Walsh). Corroborating our measure’s validity, we found that state-wide differences in name-based social status were positively associated with state-wide income levels in 1920 (p < .001).”
Once again, researchers found that people of higher social status were at a higher risk of dying from the Spanish Flu during the initial stages of the pandemic. 55 days into the pandemic, the effect reversed and lower social status was associated with a higher risk of dying in the later stages. This suggests that even 100 years ago, like today, people of higher social status had higher spatial and relational mobility.
“Taken together, our findings hint at a most relevant (and tragic) dynamic: While people of higher social status may import novel viruses and cause their initial spread, people of lower social status carry the major burden once the pandemic unfolds.”
Findings suggest that contrary to the dogma in epidemiology, during the current COVID-19 pandemic, and the Spanish Flu over 100 years ago, viruses spread faster initially among people of higher social status. Read more about the study by Jana B. Berkessel, Tobias Ebert, Jochen Gebauer, Thorsteinn Jonsson, and Shigehiro Oishi here.
