RESUMEN
The SARS-CoV-2 pandemic has led to an unprecedented daily use of molecular RT-PCR tests. These tests are interpreted qualitatively for diagnosis, and the relevance of the test result intensity, i.e. the number of amplification cycles (Ct), is debated because of strong potential biases. We analyze a national database of tests performed on more than 2 million individuals between January and November 2020. Although we find Ct values to vary depending on the testing laboratory or the assay used, we detect strong significant trends with patient age, number of days after symptoms onset, or the state of the epidemic (the temporal reproduction number) at the time of the test. These results suggest that Ct values can be used to improve short-term predictions for epidemic surveillance.
RESUMEN
In this case-control study on 564 healthcare workers of a university hospital in Paris (France), contacts without protection with COVID-19 patients or with colleagues were associated with infection with SARS-CoV-2, while working in a COVID-dedicated unit, using public transportation and having children kept in childcare facilities were not.
RESUMEN
BackgroundFrom the start of the pandemic, health-care workers (HCW) have paid a heavy toll to the coronavirus disease-19 (COVID-19) outbreak. ObjectivesTo describe the dynamics and determinants of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection in HCW. DesignProspective observational study conducted from February 24th until April 10th, 2020. SettingComparison of a 1,500-bed adult and a 600-bed pediatric setting of a tertiary-care university hospital located in central Paris. ParticipantsAll symptomatic HCW screened for SARS-CoV-2 on a nasopharyngeal swab. MeasurementsHCW screened positive were prospectively questioned on their profession, symptoms, occupational and non-occupational exposures to SARS-CoV-2. ResultsAmong 1344 symptomatic HCW tested, 373 were positive (28%) and 336 (90%) corresponding questionnaires were completed. Three hospitalizations and no death were reported. Most HCW (70%) had patient-facing occupational activities (22% in COVID-19 dedicated units). The total number of HCW cases peaked on March 23rd, then decreased slowly, concomitantly with a continuous increase of compliance to preventive measures (including universal medical masking and personal protective equipment (PPE) for direct care to COVID-19 patients). Attack rates were of 3.2% and 2.3% in the adult and pediatric setting, respectively (p=0.0022). In the adult setting, HCW more frequently reported exposure to COVID-19 patients without PPE (25% versus 15%, p=0.046). Report of contacts with children attending out-of-home care facilities dramatically decreased over the study period. LimitationsLack of COVID-19 negative controls and recall bias. ConclusionUniversal masking, reinforcement of hand hygiene, and PPE with medical masks for patients care allowed protection of HCW and containment of the outbreak. Residual transmissions were related to persistent exposures with undiagnosed patients or colleagues and not to contacts with children attending out-of-home care facilities.