EP 48 - A Case-control Study of COVID-19 Outbreaks in Dialysis Patients

Background: Japan's Ministry of Health, Labor and Welfare defines an outbreak as "five or more patients found in one place with a clear contact history." Our study focuses on a group infection (disease cluster) which occurred at an outpatient dialysis medical site in a commercial building in Odawara City, Kanagawa Prefecture. A survey was conducted to clarify the actual situation of the cluster outbreak and associated infection factors.

Methods: From April 18 to April 27, 2022, a total of 21 patients receiving outpatient hemodialysis therapy at a dialysis clinic and clinic staff members who tested positive for COVID-19 were selected as a case group. A total of 43 patients and staff who had not contracted COVID-19 during the same period were used as a control group. Basic information on the subjects was collected and analyzed using descriptive epidemiological methods. The information was divided into three elements: "time," "place," and "person." A case-control study was conducted on the exposure factors of COVID-19 patients.

Results: Eleven dialysis patients and 10 health care workers contracted COVID-19. Exposure factors identified in this study included the use of shared changing rooms after 15:00 (odds ratio = 13.07, 95% CI 1.60-106.71) and night dialysis (odds ratio = 14.55, 95% CI 1.62-130.53).

Conclusions: The dialysis clinic was a closed space with no windows, and it was suggested that the infection spread to night dialysis patients mainly through shared lockers for male patients. We believe that treatment environments for dialysis patients with a high risk of severe disease should be equipped with adequate ventilation.