Pandemic under roofs: The untold story of resilience in Hong Kong's sub-divided units

Despite there being a rich set of studies documenting the association between the built environment and the spread of COVID-19, little attention has been paid to the communities that are with informal housing. Whether the government's policy could help mitigate the risk of suffering COVID-19. Little is known about this issue. To fill this blank, we would like to consider the communities with sub-divided units (SDU) in Hong Kong. SDU is a kind of informal housing, where the appearance is due to some homeowners spontaneously subdividing their domestic flats into two or more units with small sizes to low-income tenants for making extra cash flows. On collecting the daily confirmed case of COVID-19 from the Department of Health in Hong Kong (from late November 2020 to mid-May 2021) and the SDU data from the local property agent's website, our findings reveal: initially, street blocks with SDU are more vulnerable to COVID-19, exhibiting higher case counts and more frequent compulsory testing notices (CTN) compared to non-SDU areas; subsequently, SDU areas also required a longer recovery time during the fourth wave of the pandemic, with CTN implementation not significantly hastening recovery; thirdly, a quicker response time between the first case report and CTN implementation correlated with fewer cases and shorter recovery periods, particularly when actions were taken within a shorter serial interval of less than 3.6 days; finally, re-evaluating the effectiveness of CTN based on reaction time and serial intervals suggests that adopting the serial interval as a threshold for implementation could significantly reduce the incidence in SDU areas. These insights highlight the unique challenges faced by informal housing communities during pandemics and underscore the need for tailored government policies to effectively mitigate risks.