How where you live influences the severity of Covid infection

2 Nov, 2022

By Martin Boudou

The pandemic showed that socio economic status is both an indicator of health and a driver of infection in Ireland. In March 2020, the Covid-19 pandemic revealed the inherent vulnerability of our modern society to emerging infectious diseases. Globalisation of products and high travel frequency contributed to the rapid spread of infection, particularly in densely populated urban areas.

We have conducted multiple research projects based on laboratory-confirmed infection data from the first two Covid waves (March 2020 to November 2020). Many results confirmed the findings obtained from international research. For example, the primary drivers of Covid-19 severity, defined as a passage from a symptomatic case of infection to a severe outcome (ie, hospitalisation, ICU admission, or death), are closely correlated with individual features such as patient's age (older persons are more vulnerable), gender (males are more likely to acquire severe outcomes) or the presence of underlying health conditions (including obesity, cancer or asthma).

Our findings also revealed that characteristics of the living area, and particularly the local socio-economics profile, played a driving role in the incidence and severity of Covid-19 cases in Ireland. A recent study found that Irish people living in areas with a high proportion of local authority housing and lower mean educational attainment reported an increased risk of hospitalisation upon confirmation of a Covid-19 infection from March to November 2020. The impact of socioeconomic profile of the local residential area was consistently significant.

Another project examined the emergence of Covid-19 space-time clusters of infection, whereby the observed number of cases is significantly higher than the expected number of cases during a specific period and within a specific area. This found that less affluent regions in Ireland and within the Greater Dublin Area were 1.3 and 2.3 times respectively more likely to report clusters.

In Dublin, these Covid "hotspots" were more often identified in northern and western parts of the city (see Figure 1), areas often historically associated with a lower socioeconomic status. A strong statistical link was established between these at-risk areas and the low proportion of highly qualified workers, the population with a lower level of qualification was adjudged to be more at risk since they were not able to work from home.

The impact of socio-economics on Covid-19 incidence and severity has appeared again and again throughout our projects, reflecting more general health inequalities between different population cohorts or between different neighborhoods. Similar observations have been made by international researchers: for example, researchers in Barcelona and Louisiana identified that low-income neighbourhoods had a higher relative risk of Covid-19 incidence

But what applies to Covid also applies to many other infections. Over the past number of years, we have carried out a number of projects examining several environmentally-acquired infections including Verotoxigenic Escherichia Coli, cryptosporidiosis, and campylobacteriosis, all of which have very high incidence rates in Ireland compared with European averages.

While we expected to identify environmental causes such as cattle density, geology, or rainfall as the primary drivers of disease, we also found that socio-economic status remained a strong predictor. For example, areas having a lower level of education appeared to be more at risk for cryptosporidiosis.

Conversely, findings showed that rural and commuter (urban fringe) areas with lower average levels of education were less likely to be at risk for campylobacteriosis and VTEC. One hypothesis for this lower risk in association with a higher deprivation level is linked with differing dietary habits in high-income households. Both infections can be foodborne and are more likely transmitted through eating out consumption of fresh vegetables, or undercooked meat.

There is little doubt that socio-economic status represents both an indicator of health and a driver of infection in Ireland. Our research findings highlight the need for a higher level of risk education, particularly around the transmission of these diseases. There is an urgent need to raise awareness of foodborne diseases such as campylobacteriosis or VTEC, with recommendations for carefully washing vegetables or cooking meats.

Similarly, the higher concentration of Covid-19 infections in less affluent areas of Dublin reflects that the pandemic exacerbated existing socio-economic inequalities. It shows the need for focused public health strategies and interventions, with a specific focus on areas where people do not have the capacity to work from home and are therefore more exposed to the virus.

The Spatio-Temporal Environmental Epidemiology Research Group (STEER) is based between TU Dublin and UCC

This article was first published on RTE Brainstorm