Abstract

Shared ablutions and stairwells, corridor cross-ventilation and non-deliberate perflation (natural draft blowing through a space) are potential risk factors for COVID-19 transmission in corridor-based accommodation. This paper uses retrospective spatial analysis to identify potential built environmental risk factors during the January–March 2021 outbreak in Victory College, Royal Military Academy Sandhurst.

Distance was measured in units of single room spacing. Odds, ORs and 95% CIs were calculated to identify and measure associations between distance from exposure and having COVID-19. Distance response trends were assessed using Pearson’s χ² for trend test. Linear relationships were tested using the t-test or rank-sum test.

Stairwells and ablutions were not identified as likely sources of infection for all corridor occupants. Assuming occupants used their nearest ablutions, closer distance among those attributed to using ablutions 2 (one of four sets of ablutions), was identified as a risk factor (p=0.05). Testing distance response by χ² linear trend testing showed a potential association between nearest adjacent positive room and COVID-19 (p=0.06), strongest if dominant air movement along the corridor length was from the left (p=0.10) compared with the right (p=0.24).

Formal qualitative spatial analysis and environmental assessment of ventilation and air movement has a role in outbreak investigation in assessing factors related to the built environment. Environmental investigations would best inform outbreak investigations if undertaken contemporaneously. Pre-emptive and retrospective studies can help inform public health advice to military establishments in business continuity planning for isolation facilities, during outbreaks or in future development of the built environment.