OBJECTIVE: We sought to contain a healthcare-associated coronavirus disease 2019 (COVID-19) outbreak, to evaluate contributory factors, and to prevent future outbreaks .

DESIGN: Quasi-experimental cluster-control outbreak evaluation .

METHODS: All patients and staff on the outbreak ward (case cluster), and randomly selected patients and staff on COVID-19 wards (positive control cluster) and a non-COVID-19 wards (negative control cluster) underwent reverse-transcriptase polymerase chain reaction (RT-PCR) testing . Hand hygiene and personal protective equipment (PPE) compliance, detection of environmental SARS-COV-2 RNA, patient behavior, and SARS-CoV-2 IgG antibody prevalence were assessed .

RESULTS: In total , 145 staff and 26 patients were exposed, resulting in 24 secondary cases . Also , 4 of 14 (29 %) staff and 7 of 10 (70 %) patients were asymptomatic or presymptomatic . There was no difference in mean cycle threshold between asymptomatic or presymptomatic versus symptomatic individuals . None of 32 randomly selected staff from the control wards tested positive . Environmental RNA detection levels were higher on the COVID-19 ward than on the negative control ward (OR , 19.98; 95% CI , 2.63-906.38; P <.001). RNA levels on the COVID-19 ward (where there were no outbreaks) and the outbreak ward were similar (OR , 2.38; P = .18). Mean monthly hand hygiene compliance, based on 20,146 observations (over preceding year), was lower on the outbreak ward (P <.006). Compared to both control wards, the proportion of staff with detectable antibodies was higher on the outbreak ward (OR , 3.78; 95% CI , 1.01-14.25; P = .008).

CONCLUSION: Staff seroconversion was more likely during a short-term outbreak than from sustained duty on a COVID-19 ward . Environmental contamination and PPE use were similar on the outbreak and control wards . Patient noncompliance, decreased hand hygiene, and asymptomatic or presymptomatic transmission were more frequent on the outbreak ward.