Investigation of healthcare-associated COVID-19 in a large French hospital group by whole-genome sequencing

Objectives: Despite the quick implementation of infection prevention and control procedures and the use of personal protective equipment within healthcare facilities, many cases of nosocomial COVID-19 transmission have been reported. We aimed to estimate the frequency and impact of healthcare-associated COVID-19 (HA-COVID-19) and evaluate the contribution of whole-genome sequencing (WGS) in cluster investigation.

Methods: We estimated the frequency and mortality of HA-COVID-19 infections from September 1 to November 30, 2020, with a focus on the evolution of hospitalized community-associated COVID-19 (CA-COVID-19) cases and cases detected among healthcare workers (HCWs) within the Sorbonne University Hospital Group (Paris, France). We thoroughly examined 12 clusters through epidemiological investigations and WGS.

Results: Overall, 209 cases of HA-COVID-19 were reported. Evolution of HA-COVID-19 incidence closely correlated with the incidence of CA-COVID-19 and COVID-19 among HCWs. During the study period, 13.9 % of hospitalized patients with COVID-19 were infected in the hospital and the 30-day mortality rate of HA-COVID-19 was 31.5 %. Nosocomial transmission of SARS-CoV-2 led to clusters involving both patients and HCWs. WGS allowed the exclusion of one-third of cases initially assigned to a cluster.

Conclusions: WGS analysis combined with comprehensive epidemiological investigations is essential to understand transmission routes and adapt the IPC response to protect both patients and HCWs.