[Epidemiology and risk factors of nosocomial COVID infections in the Service of internal medicine at CHUV]

Nosocomial COVID-19 infections are a challenge for hospitals. In order to assess possible demographic, personal, environmental or medical care related risk factors, data of nosocomial cases occurring in the Service of internal medicine at CHUV between February and March 2021 were retrospectively analyzed. Neither personal nor medical care related factors were identified as risk factor for a nosocomial infection. However, a significant number of patients with hospital-acquired COVID infection stayed in a 5-bed ward (versus 1-2 beds) and shared toilets in these rooms. Patient distancing measures and weekly screening led to a subsequent significant reduction of nosocomial SARS-CoV-2 infections.

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!.

Control of nosocomial transmission of SARS-COV-2 in the service of internal medicine in Lausanne university hospital

Introduction: Transmission of SARS-CoV-2 inside the hospital has significant implications for patients and healthcare workers. Objectives: We describe a nosocomial outbreak of SARS-CoV-2 infections in the Service of Internal Medicine, the implemented infection prevention and control (IPC) measures and their impact. Methods: We report all consecutive nosocomial cases in a 206-bed service from February 8 until April 8, 2021 (weeks 6-14). Nosocomial COVID-19 cases were defined as microbiologically documented cases by PCR, diagnosed ≥ 5 days after admission. A cluster was defined based on the detection of ≥ 2 nosocomial COVID-19 cases within a given period (< 72 h) or geographically linked. IPC measures implemented on week 10 to control SARS-CoV-2 transmissions in all non- COVID units were: systematic screening at day 3 after admission;weekly screening of all patients by PCR on saliva;and decreasing the occupancy of all patient rooms with 5 patients to 3. Results: 69 cases were identified, with 57 attributed to 21 clusters and 12 cases considered isolated. Median age was 74 years (IQR 65, 80) and 40.6% were female. All cases had a previous negative test and median time from admission to positive test was 12 days (IQR 8, 17). 45.1% of nosocomial cases were completely asymptomatic. 60.9% of patients stayed in rooms with 5-patients. Death occurred in 23.2% of cases. The incidence of nosocomial cases was the highest between weeks 8 and 10 with 18 and 17 new cases per week, respectively. After the introduction of IPC measures on week 10, there was a rapid decrease in the number of cases until complete absence of new cases on week 14. Conclusion: Nosocomial infections were frequently asymptomatic, potentially hampering fast diagnosis which is crucial for control of transmission, and were associated with high mortality rate. The implementation of additional IPC measures led to a gradual decrease in nosocomial transmissions and allowed controlling the outbreak.

Nosocomial transmission of SARS-COV-2: experience from the contact tracing activity of the infection control unit for the university hospital of lausanne

Introduction: The high transmissibility of SARS-CoV-2 is of particular concern for hospitals as hospitalized patients are at risk of severe COVID-19 and related death. Objectives: Describe the contact tracing activity related to nosocomial SARS-CoV-2 cases in our hospital. Methods: The Infection Control Unit received alerts for positive PCR results performed by the Microbiology laboratory in hospitalized patients. Nosocomial infections, occurring after at least 5 days of hospitalization, were further investigated. Contact tracing was performed via an institutional software allowing tracing index patients' movements and their roommates. Patients were considered “contacts” at risk and were placed in quarantine if they shared the same room with the index-case up to 72 h before index's first positive PCR or first symptoms. Contacts systematically had nasopharyngeal SARS-CoV-2 PCR testing at days 0, 10 counting from last contact with the index or at symptom onset. Results: Between November 1st 2020 until March 31st 2021, 322 nosocomial SARS-CoV-2 cases were identified, of whom 195 (61%) had previously been in contact with another known case while for 127 (39%) source of infection was unknown. Median time from admission to positive PCR was 13 days (IQR 8 - 25). Symptoms where present in 67% of cases. Median age was 76 years (IQR 64 - 84). Of all episodes, 75% were diagnosed in medical units (including 50 cases, 16% in geriatric sections),24% in surgical sectors and 1% in the ICU. Contact tracing activity identified 605 contacts with a median of 2 contacts per index case (range 0-19). Of these, 32% had a positive PCR result during follow-up. Conclusion: A thorough contact tracing with systematic PCR screening is necessary after detection of a nosocomial SARS-CoV-2 case as transmissibility is high and more than 1/3 of cases are asymptomatic. The non-identification of a source for more than a third of cases raises concerns of potential implication of healthcare workers in transmission.

Implementing SARS-CoV-2 Rapid Antigen Testing in the Emergency Ward of a Swiss University Hospital: The INCREASE Study

Following the Swiss Federal Office of Public Health (FOPH) authorization of the rapid antigen test (RAT), we implemented the use of the RAT in the emergency ward of our university hospital for patients' cohorting. RAT triaging in association with RT-PCR allowed us to promptly isolate positive patients and save resources. Among 532 patients, overall sensitivities were 48.3% for Exdia and 41.2% for Standard Q^R, Panbio^TM and BD Veritor TM. All RATs exhibited specificity above 99%. Sensitivity increased to 74.6%, 66.2%, 66.2% and 64.8% for Exdia, Standard Q^R, Panbio^TM and BD Veritor TM, respectively, for viral loads above 10⁵ copies/mL, to 100%, 97.8%, 96.6% and 95.6% for viral loads above 10⁶ copies/mL and 100% for viral loads above 10⁷ copies/mL. Sensitivity was significantly higher for patients with symptoms onset within four days (74.3%, 69.2%, 69.2% and 64%, respectively) versus patients with the evolution of symptoms longer than four days (36.8%, 21.1%, 21.1% and 23.7%, respectively). Among COVID-19 asymptomatic patients, sensitivity was 33%. All Immunoglobulin-A-positive patients resulted negative for RAT. The RAT might represent a useful resource in selected clinical settings as a complementary tool in RT-PCR for rapid patient triaging, but the lower sensitivity, especially in late presenters and COVID-19 asymptomatic subjects, must be taken into account.