An outbreak of SARS-CoV-2 in a public-facing office in England

Managing SARS-CoV-2 transmission risk in workplace COVID-19 outbreaks

OBJECTIVES

A Coronavirus disease 2019 (COVID-19) workplace outbreak is a risk to the health of workers and business continuity. To minimise this risk, companies have implemented risk management measures (RMMs) designed to mitigate SARS-CoV-2 transmission within the workforce. The objective of this work was to gather insights into the application of RMMs in non-healthcare workplaces and to improve understanding of the practical barriers to their implementation.

METHODS

Data were collected using a pre-designed framework from 12 volunteer workplaces through discussions with staff responsible for site safety and during site visits to observe the RMMs and work processes. To evaluate ventilation effectiveness, measurements for carbon dioxide (CO2) were taken during the site visit and logged over an extended period in selected occupied areas.

RESULTS

RMMs that were implemented well included working at home for office and other non-production staff, provision, and use of face coverings, provision for hand hygiene, and as methods became commonly available, carrying out testing for infected people. However, maintaining adequate physical distancing in many production areas proved difficult because established factory layouts cannot be easily changed and there is often a need for workers to be close to each other to communicate. A major shortcoming identified was the understanding and application of measures to improve workplace ventilation. Rapidly installing and/or upgrading mechanical ventilation systems during a pandemic may not be practical and ideally should be considered in building design. Measuring CO2 in occupied workspaces proved to be a useful tool for identifying areas with potentially inadequate ventilation.

CONCLUSIONS

Preventing workplace attendance by identifying infected individuals is challenging, making effective RMMs crucial to mitigating virus transmission. The effectiveness of individual RMMs can be uncertain; therefore, it is necessary to adopt multilayered RMMs. Successful implementation relies on measures that are specific to individual workplaces, identified by accurate risk assessment, regularly reviewed for effectiveness, and worker compliance. Establishing suitable risk mitigation policies and providing staff supervision are vital to ensure the sustained and effective implementation of RMMs. For RMMs that require technical understanding, such as workplace ventilation systems, specialist support may be necessary to ensure effective implementation.

A SARS-CoV-2 outbreak in a public order and safety training facility in England, June 2021

BACKGROUND

The public order and safety (POS) sector remains susceptible to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreaks, as workplace attendance is typically compulsory and close physical contact is often needed. Here, we report on a SARS-CoV-2 outbreak with an attack rate of 39% (9/23), which occurred between 19 and 29 June 2021 among a cohort of new POS recruits participating in a mandatory 18-week training programme in England.

METHODS

The COVID-OUT (COVID-19 Outbreak investigation to Understand Transmission) study team undertook a multidisciplinary outbreak investigation, including viral surface sampling, workplace environmental assessment, participant viral and antibody testing, and questionnaires, at the two associated training facilities between 5 July and 24 August 2021.

RESULTS

Environmental factors, such as ventilation, were deemed inadequate in some areas of the workplace, with carbon dioxide (CO2) levels exceeding 1,500 ppm on multiple occasions within naturally ventilated classrooms. Activities during safety training required close contact, with some necessitating physical contact, physical exertion, and shouting. Furthermore, most participants reported having physical contact with colleagues (67%) and more than one close work contact daily (97%).

CONCLUSIONS

Our investigation suggests that site- and activity-specific factors likely contributed to the transmission risks within the POS trainee cohort. Potential interventions for mitigating SARS-CoV-2 transmission in this POS training context could include implementing regular rapid lateral flow testing, optimizing natural ventilation, using portable air cleaning devices in classrooms, and expanding use of well-fitted FFP2/FFP3 respirators during activities where prolonged close physical contact is required.

Risk factors for SARS-CoV-2 infection at a UK electricity-generating company: a test-negative design case-control study

OBJECTIVES

Identify workplace risk factors for SARS-CoV-2 infection, using data collected by a UK electricity-generating company.

METHODS

Using a test-negative design case-control study, we estimated the OR of infection by job category, site, test reason, sex, vaccination status, vulnerability, site outage and site COVID-19 weekly risk rating, adjusting for age, test date and test type.

RESULTS

From an original 80 077 COVID-19 tests, there were 70 646 included in the final analysis. Most exclusions were due to being visitor tests (5030) or tests after an individual first tested positive (2968).Women were less likely to test positive than men (OR=0.71; 95% CI 0.58 to 0.86). Test reason was strongly associated with positivity and although not a cause of infection itself, due to differing test regimes by area, it was a strong confounder for other variables. Compared with routine tests, tests due to symptoms were highest risk (94.99; 78.29 to 115.24), followed by close contact (16.73; 13.80 to 20.29) and broader-defined work contact 2.66 (1.99 to 3.56). After adjustment, we found little difference in risk by job category, but some differences by site with three sites showing substantially lower risks, and one site showing higher risks in the final model.

CONCLUSIONS

In general, infection risk was not associated with job category. Vulnerable individuals were at slightly lower risk, tests during outages were higher risk, vaccination showed no evidence of an effect on testing positive, and site COVID-19 risk rating did not show an ordered trend in positivity rates.