Outbreaks of seasonal OC43 coronavirus with nosocomial transmission during COVID-19 pandemic setting: when a coronavirus hides another

Introduction: Management and control of COVID-19 outbreaks in hospital settings represent a major challenge. Any suspicion of nosocomial transmissions require prompt investigations and control measures. Objectives: To describe the management of 2 consecutive clusters of patients presenting suspect symptoms of Covid-19 in a 19-bed psychogeriatric unit, hosting concomitantly 2 patients with SARS-CoV-2 infection confirmed by RT-PCR on nasopharyngeal swabs (lineage B.1.1.7, viral loads of 6.9E + 8 and 8.0E + 7 copies/ml, respectively) among whom one was a nosocomial case with persistence of a high viral load at day 14 (8.9E + 6 copies/ml). Methods: After identification of the SARS-CoV-2 cases, control measures were promptly applied. During the following weeks, the clinicians of the ward additionally reported 2 clusters of 3 patients with suspect symptoms. All of these suspect cases were isolated with Droplet Precautions and were investigated by a nasopharyngeal swab for SARSCoV- 2 testing. If the first SARS-CoV-2 RT-PCR was negative, a second test was performed within 24 h. Additionally, we proposed to complete investigations by an extended respiratory multiplex RT-PCR. Results: Among the 6 symptomatic patients, all had 2 consecutively negative SARS-CoV-2 RT-PCR. The respiratory virus panel test revealed a positive PCR for OC43 coronavirus in 5/6 patients, with viral load ranging from 3E + 5 to 3E + 9 copies/ml, confirming a nosocomial outbreak of a seasonal coronavirus. For the remaining patient, infection by OC43 coronavirus was considered possible, regarding the close contacts with positive cases during the hospital stay. Conclusion: Even if the actual Covid-19 epidemic setting should conduct to promptly research a SARS-CoV-2 infection in symptomatic hospitalized patients, this report highlights the possibility of cocirculation of different respiratory virus within the same ward. More extended microbiological investigations with specific RT-PCR analysis in symptomatic patients repeatedly tested negative for Covid-19, can conduct to a better understanding of nosocomial outbreaks. Sometimes a coronavirus can hide another!.