The GHQ-12 is a 12-item self-report measure devised to screen for psychological distress in the general population.29 The measure has high specificity and sensitivity, with reliability demonstrated across a range of populations.30 31 The GHQ-12 has been used in similar clinician-based studies measuring the psychological impact of infectious outbreaks and was chosen due to the brevity of the measure and its suitability for time-pressured medical staff.21 The GHQ-12 assesses current state and asks the participants to compare with usual state. GHQ-12 was asked at all three survey phases. Case-level distress is defined as a score of >3.30