Risk of Infections Among Contacts of COVID-19 Cases in the Healthcare Setting: Experience of One University Hospital

Background/Objectives: The onset of infection in patients in contact with a COVID-19-positive index case in healthcare settings depends on intrinsic factors such as demographic factors, immune status, severity of underlying diseases, and comorbidities. Critical extrinsic factors for transmission, especially in hospitals, are length of exposure and distance. This study aimed to determine the risk factors of COVID-19 infections in contacts of COVID-19 index cases by conducting a prospective cohort study. Methods: The prospective cohort study included 186 index patients with confirmed COVID-19 and their 416 close hospital contacts. All contacts were followed for five days and tested using antigen or RT-PCR assays, with additional follow-up through national registries if discharged earlier. Results: The risk of infection was significantly higher in contacts older than 60 years (p = 0.009), in those hospitalised within orthopaedics and haematology departments (p < 0.001), and in patients whose bed was located within 1.5 m of the index case (p < 0.001). Laboratory findings showed significant associations with lower lymphocytes, glucose and higher potassium and creatinine levels, while other haematological and biochemical parameters did not differ. Hyperkalaemia (RR = 6.2 95%CI = 1.2–32.1 p = 0.30) and bed distance ≥ 1.5 m (RR = 0.3 95%CI = 0.2–0.6 p < 0.001) demonstrated an independent association with COVID-19 infection among contact patients. Conclusions: To reduce nosocomial transmission from unrecognised COVID-19 reservoirs, patients with electrolyte imbalance and lower levels of blood elements should be placed at a greater distance of 1.5 m from others, especially patients in haematology departments.