January 23, 2023

The first COVID-19 case in Singapore was reported on 23 January, 2020. In order to contain the spread of the virus, prompt hotspot identification and transmission risk assessment are critical for public health.

In ‘Impact of urbanisation and environmental factors on spatial distribution of COVID‑19 cases during the early phase of epidemic in Singapore’ (Scientific reports, 2022), Dr Murali Krishna Gurram, Ms Min Xian Wang, Visiting Assistant Professor Junxiong Pang (all NUS Saw Swee Hock School of Public Health), and Associate Professor Yi‑Chen Wang (NUS Geography) explore how environmental and urbanisation factors influence the transmission of COVID-19 during the early phase of the pandemic in Singapore.

Firstly, temperature seems to affect how fast the virus spreads. Drawing residential location and other information from government databases, the authors observe that the environment is most favourable for virus transmission when the temperature is between 27.5 °C and 28.5 °C. However, there was no further evidence to suggest that hotter weather will lead to a drop in COVID-19 cases.

Nevertheless, the authors postulate that it is theoretically possible for the virus to be less transmissible in hot weather. Contaminated droplets can travel a shorter distance in dry air, and people also tend to reduce outdoor travelling when the temperature is high.

Secondly, more densely populated regions are likely to have faster spread of the virus. The authors found that densely populated regions are more likely to be visited by COVID-19 patients. Furthermore, the presence of imported cases in a neighbourhood is closely linked to the occurrence of new local cases within the same community. This could be because the family members of those infected with COVID-19 overseas could still move around freely before developing symptoms, thus leading to pre-symptomatic transmissions.

The authors conclude the study by suggesting that high population density and urbanisation level (measured by the proportion of built-up areas in the region) are associated with high risk of COVID-19 transmissions. Thus, regions with such risk factors should receive stronger public health surveillance.

Read the article here: https://www.nature.com/articles/s41598-022-12941-8