Risk of COVID-19 in Health Professionals: A Case-Control Study, Portugal

Introduction: Health professionals face higher occupational exposure to SARS-CoV-2. We aimed to estimate the risk of COVID-19 test positivity in health professionals compared to non-health professionals. Methods: We conducted a test-negative case-control study using Portuguese national surveillance data (January to May 2020). Cases were suspected cases who tested positive for SARS-CoV-2;controls were suspected cases who tested negative. We used multivariable logistic regression modelling to estimate the odds ratio of a positive COVID-19 test (RT-PCR;primary outcome), comparing health professionals and non-health professionals (primary exposure), and adjusting for the confounding effect of demographic, clinical, and epidemiological characteristics, and the modification effect of the self-reported epidemiological link (i.e., self-reported contact with a COVID-19 case or person with COVID-19-like symptoms). Results: Health professionals had a 2-fold higher risk of a positive COVID-19 test result (aOR = 1.89, 95% CI 1.69-2.11). However, this association was strongly modified by the self-report of an epidemiological link such that, among cases who did report an epidemiological link, being a health professional was a protective factor (aOR = 0.90, 95% CI 0.82-0.98). Conclusion: Our findings suggest that health professionals might be primarily infected by unknown contacts, plausibly in the healthcare setting, but also that their occupational exposure does not systematically translate into a higher risk of transmission. We suggest that this could be interpreted in light of different types and timing of exposure, and variability in risk perception and associated preventive behaviours.

Nosocomial COVID-19: experience from a large acute NHS Trust in South-West London.

Transmission of coronavirus disease 2019 (COVID-19) in healthcare settings has significant implications for patients and healthcare workers, may amplify local outbreaks, and may place additional burden on already stretched resources. Risk of missed or late diagnosis of COVID-19 was high during the UK's initial 'containment phase', because of strict criteria for testing. The risk remains due to asymptomatic/pre-symptomatic transmission, complicated by challenges faced with laboratory testing. We present a case study of potential nosocomial transmission associated with the first case of COVID-19 at a large acute NHS Trust in South-West London, and we describe the prevailing burden of nosocomial infections.