Laboratory evaluation of a quaternary ammonium compound (QAC)-based antimicrobial coating used in public transport during the COVID-19 pandemic (preprint)

The virucidal activity of a quaternary ammonium compound (QAC)-based antimicrobial coating used by the UK rail industry during the COVID-19 pandemic was evaluated using the bacteriophage {Phi}6 as a surrogate for SARS-CoV-2. Immediately after application and in the absence of interfering substance, the product showed efficacy (>3 log10 reduction) on some materials typically used in rail carriages (stainless steel, high pressure laminate and plastic), variable efficacy on glass and no efficacy (<3 log10 reduction) on a train armrest made of Terluran 22. If, after application of the product, the surfaces remained undisturbed, the antimicrobial coating retained its efficacy for at least 28 days on all materials where it was effective immediately after application. However, regardless of the material coated or time since application, the presence of organic debris (fetal bovine serum) significantly reduced the viricidal activity of the coating. Wiping the surface with a wetted cloth after organic debris deposition was not sufficient to restore efficacy. We conclude that the product is likely to be of limited effectiveness in a busy multi-user environment such as public transport.

Social risk factors for SARS-CoV-2 acquisition in University students: cross sectional survey (preprint)

Objectives To define risk factors for SARS-CoV-2 infection in University of Cambridge students during a period of increased incidence in October and November 2020. Study design Survey Methods Routine public health surveillance identified a marked increase in the numbers of University of Cambridge students with respiratory illness and SARS-CoV-2 positivity in the 10 days after a national lockdown was announced in the UK on 5 November 2020. Cases were identified both through symptom-triggered testing and a universal asymptomatic testing program. An online questionnaire was sent to all University of Cambridge students on 25 November to investigate risk factors for testing positive in the period after 30 October 2020. This asked about symptoms, SARS-CoV-2 test results, in-person teaching settings, other aspects of University life, and attendance at social events in the period just prior to lockdown, from 30th October and 4th November 2020. Univariate and multivariable analyses were undertaken evaluating potential risk factors for SARS-CoV-2 positivity. Results Among 3,980 students responding to the questionnaire, 99 (2.5%) reported testing SARS-CoV-2 positive in the period studied; 28 (28%) were asymptomatic. We found strong independent associations with SARS-CoV-2 positivity were attendance at two social settings in the City of Cambridge (adjusted odds ratio favouring disease 13.0 (95% CI 6.2,26.9) and 14.2 (95% CI 2.9,70)), with weaker evidence of association with three further social settings. By contrast, we did not observe strong independent associations between disease risk and type of accommodation or attendance at, or participation in, a range of activities associated with the University curriculum. Conclusions Attendance at social settings can facilitate widespread SARS-CoV-2 transmission in University students. Constraint of transmission in higher education settings needs to emphasise risks outside University premises, as well as a COVID-safe environment within University premises.