were classified as PUI for COVID-19, but contact tracing was not required as they had been home quarantined compulsorily on arrival. Gate screening was also made compulsory for foreign tourists during the alert phase. They must register at the gate and perform health screening including temperature checks, and prohibitions were initiated at buildings such as the mosque and child health centers to prevent mass infection and protect vulnerable populations. Information was given in several languages, depending on the target population.

The university health centre heightened in importance during the COVID-19 alert phase. In addition to normal daily operation, it was responsible for training of medical professionals, balancing medical equipment and PPE stocks, establishing zones in health centre to minimize exposure to COVID-19 among health professionals, performing health screening andMeasurement of the HR profile and quality control

The UK Biobank is a cohort of individuals with an age range of 40–69 registered with a general practitioner of the UK National Health Service. In total 503,325 individuals were included and provided informed consent between 2006 and 2010. The UK Biobank cohort study was approved by the North West Multi-centre Research Ethics Committee (reference number 06/MRE08/65). Detailed methods used by UK Biobank have been described elsewhere45.

In total, 99,539 ECG exercise records were taken for 96,567 participants who underwent a cardio assessment; 79,217 were performed during the baseline visit (2006–2010), and 20,322 were performed at the second follow-up visit (2012–2013). The participants were asked to sit on a stationary bike, start cycling after 15 s of rest, and then perform six