Abstract
OBJECTIVE: To describe the public health response to COVID-19 within a large prison with a high number of clinically vulnerable residents. DESIGN: An outbreak investigation was undertaken among all residents and staff. A screening event involved nose and throat swab samples from residents and staff, examined by polymerase chain reaction (PCR). An electronic questionnaire regarding risk factors was distributed to staff. RESULTS: 58 residents out of 1,156 (5.0%, 95% CI: 3.8 - 6.3) and 129 staff out of 510 (25.3%, 95% CI: 21.5 - 29.1) displayed COVID-19 symptoms, including six and eight confirmed, respectively. Residents reported cough symptoms with no fever (29.3%), followed by a cough and fever (15.5%). 62.1% of symptomatic residents were 50 years or older, placing them in the group at risk for severe COVID-19 disease. Wing I had the highest attack rate (12.5%). 1,063 individuals were swabbed during the 5-day screening event, and all had negative swab results. CONCLUSION: The findings were consistent with the hypothesis of a propagating outbreak with decreasing incidence since the peak date of onset. COVID-19 transmission within a high-risk setting was quickly contained, and an explosive outbreak was prevented through a multi-agency public health response.