A vulnerability-based approach to human-mobility reduction for countering COVID-19 transmission in London while considering local air quality

Manu Sasidharan; Ajit Singh; Mehran Eskandari Torbaghan; Ajith Kumar Parlikad

The current outbreak of novel coronavirus COVID-19 or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in the World Health Organization (WHO) declaring it as a global pandemic [1] . Reported first within the city of Wuhan, Hubei Province of China in December 2019, the COVID-19 exhibits high human-to-human transmissibility and has spread rapidly across the world [2] . The human-to-human transmission of COVID-19 can occur from 30 individuals in the incubation stage or showing symptoms, and also from asymptomatic individuals who remain contagious [3] . The COVID-19 has been reported to transmit via the inhalation of exhaled respiratory droplets [4] that remain airborne for up to 3 hours [5] . The long-term exposure to air pollution has been reported to increase the risk of experiencing severe COVID-19 outcomes [6] . The extent to which COVID-19 induces respiratory stress in infected individuals may also be 35 influenced by underlying respiratory conditions [7] like acute respiratory inflammation, asthma and cardiorespiratory diseases [8] . The simultaneous exposure to air pollutants such as particulate matter (PM) and Nitrogen dioxide (NO2) alongside COVID-19 virus is expected to exacerbate the level of COVID-19 infection and risk of fatality [9, 10] . Moreover, the adsorption of the COVID-19 virus on PM could also contribute to long-range transmission of the virus [4] . For example, the 40 2003 severe acute respiratory syndrome coronavirus 1 (SARS-CoV-1) infected patients who lived in moderate air pollution levels were reported to be 84% more likely to die than those in regions with lower air pollution [11] . The aerosol and surface stability of the COVID-19 or SARS-CoV-2 is reported to be similar to that of SARS-CoV-1 [5] . 5 Given the limited understanding of the epidemiology of COVID-19, social-distancing and humanmobility reduction measures can contribute greatly to tailoring public health interventions [12] . Consequently, countries across the world have enforced lockdowns and other coordinated efforts to reduce human-mobility [13, 14, 15, 16] . The UK's national framework for responding to a pandemic states that public transport should continue to operate normally during a pandemic, but 10 users should adopt good hygiene measures, and stagger journeys where possible [17] . Within the UK, London has recorded the highest COVID-19 related fatalities (i.e. 30.2% of UK's deaths as of 31 March 2020) [18] . On 18 March 2020, further to the UK government's advice, Transport for London (TfL) closed 40 out of 270 London Underground (LU) stations that do not serve as interchanges with other lines and announced a reduced service across its network [19] . This is also 15 because 30% of TfL's drivers, station staff, controllers and maintenance teams were not able to come to work, including those self-isolating or ill with COVID-19 [20] . The UK's current humanmobility reduction response reflects the need to maintain business continuity, near normal functioning of society and enable critical workers to make essential journeys [17, 21] . However, a statistically significant association exists between human-mobility through public transport and 20