Comparing the Impact of Road Networks on COVID-19 Severity between Delta and Omicron Variants: A Study Based on Greater Sydney (Australia) Suburbs

Abstract

The Omicron and Delta variants of COVID-19 have recently become the most dominant virus strains worldwide. A recent study on the Delta variant found that a suburban road network provides a reliable proxy for human mobility to explore COVID-19 severity. This study first examines the impact of road networks on COVID-19 severity for the Omicron variant using the infection and road connections data from Greater Sydney, Australia. We then compare the findings of this study with a recent study that used the infection data of the Delta variant for the same region. In analysing the road network, we used four centrality measures (degree, closeness, betweenness and eigenvector) and the coreness measure. We developed two multiple linear regression models for Delta and Omicron variants using the same set of independent and dependent variables. Only eigenvector is a statistically significant predictor for COVID-19 severity for the Omicron variant. On the other hand, both degree and eigenvector are statistically significant predictors for the Delta variant, as found in a recent study considered for comparison. We further found a statistical difference (p < 0.05) between the R-squared values for these two multiple linear regression models. Our findings point to an important difference in the transmission nature of Delta and Omicron variants, which could provide practical insights into understanding their infectious nature and developing appropriate control strategies accordingly.

Keywords: COVID-19 severity; delta variant; network analysis; omicron variant; suburban road network.

Figure 1

An example of the suburban road network among nine suburbs. This network is a small segment of the entire suburban road network considered in this study. The complete suburban network for the whole study region is presented in Figure 2.

Figure 2

The suburban road network for the entire study area of 137 postal areas. The node size is set according to their degree centrality values. The edge weight between two suburbs is proportionate to the number of roads connecting them.

Figure 3

Feature importance results from the random forest regression for (a) severity for Delta variant and (b) severity for Omicron variant.