key: cord-0803067-hayrhwok
authors: Lhopitallier, Loic; Brahier, Thomas; Opota, Onya; Kronenberg, Andreas; Mueller, Yolanda; Hügli, Olivier; Jaton, Katia; Boillat-Blanco, Noémie
title: No evidence of SARS-CoV-2 circulation before the identification of the first Swiss SARS-CoV-2 case.
date: 2020-07-16
journal: Int J Antimicrob Agents
DOI: 10.1016/j.ijantimicag.2020.106100
sha: c3700e0931108ee147d9242a0c2a31ae9a5a6283
doc_id: 803067
cord_uid: hayrhwok

• We performed retrospectively RT-PCR for SARS-CoV-2 on frozen naso-pharyngeal swabs of patients with lower respiratory tract infections collected in Western Switzerland between November 2019 and March 2020. • We did not identify any case before the first officially diagnosed cases; • This may suggest that the targeted screening approach was adequate when faced with a difficulties in upscaling testing capacity.

No evidence of SARS-CoV-2 circulation before the identification of the first Swiss SARS-CoV-2 case.

Loic Lhopitallier # , Thomas Brahier # , Onya Opota, Andreas Kronenberg, Yolanda Mueller, Olivier Hügli, Katia Jaton * , Noémie Boillat-Blanco* #equal contribution to this work *equal contribution to this work Highlights  We performed retrospectively RT-PCR for SARS-CoV-2 on frozen naso-pharyngeal swabs of patients with lower respiratory tract infections collected in Western Switzerland between November 2019 and March 2020.  We did not identify any case before the first officially diagnosed cases  This may suggest that the targeted screening approach was adequate when faced with a difficulties in upscaling testing capacity Dear Editor,

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic globally spread from China in a very short time. Undetected infectious individuals shed the virus in the population and contribute substantially to its dissemination [1] . Rapid identification and isolation of cases as well as contact tracing is part of the World Health Organization's recommendations to fight the outbreak.

We read with attention the paper by Deslandes et al. [2] reporting a case of retrospectively Hospital (Western Switzerland).

Using previously described methods [4, 5] , we retrospectively performed SARS-CoV-2 RT-PCR using the COBAS SARS-CoV-2 test (Roche) on naso-pharyngeal swabs collected prospectively following a standardized procedure and stored at -80°C. We included 144 patients from primary care and 30 patients from the ED who attended care between November and February 2020. Table 1 We then compared the characteristics of patients included in the ED in the period before the first Swiss positive SARS-CoV-2 patient and during the outbreak to ensure that our inclusion criteria would capture COVID-19 patients. Of note, we stopped recruiting patients in primary care for ethical reasons after the first Swiss case. During the Swiss outbreak period, 134 additional patients were included in the ED cohort and routinely tested for SARS-CoV-2 ( Table 1) . Out of them, 87 (65%) tested positive for SARS-CoV-2 between March and May 2020. Patients included in the ED during the outbreak were significantly younger (mean age of 64 years (SD 18)) compared with patients included before the outbreak (mean age 74 years, SD 15), p<0.001). Sex distribution and duration of symptoms were similar between the two groups while patients included during the outbreak had more often fever (72% versus 43%, p=0.001) and infiltrate on chest X-ray (69% versus 38%, p=0.019).

The same differences were identified when comparing SARS-CoV-2 infected patients with patients included in the ED before the first case.

In our studies, we included patients using a clinical syndromic approach (acute respiratory tract infection) and with a lower disease severity compared to the French study which included patients with ILI and radiologic abnormalities in the ICU [2] . Although, the pre-test probability for COVID-19

was possibly lower in our study population, we identified SARS-CoV-2 infected patients (87/134, 65%) using the same inclusion criteria in the ED during the outbreak, suggesting that we targeted appropriate patients. Unfortunately, we could not include patients in primary care during the outbreak and could not prove that our inclusion criteria were optimal. We observed a higher proportion of females in the primary care cohort whereas a higher representation of males is expected in SARS-CoV-2 infected patients.

Although these results are subject to selection bias, the fact that we did not retrospectively identify cases suggests that there was no or only limited ongoing human transmission of SARS-CoV-2 in Western Switzerland before March 2 nd 2020.

Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (SARS-CoV-2)

SARS-CoV-2 was already spreading in France in late

Procalcitonin and lung ultrasonography point-of-care testing to decide on antibiotic prescription in patients with lower respiratory tract infection in primary care: protocol of a pragmatic cluster randomized trial

Comparison of SARS-CoV-2 RT-PCR on a high-throughput molecular diagnostic platform and the cobas SARS-CoV-2 test for the diagnostic of COVID-19 on various clinical samples

Detection of 2019 novel coronavirus (2019-nCoV) by real-time RT-PCR

We thank all the patients who accepted to participate and make this study possible. We thank all healthcare workers of the emergency department, internal medicine ward, infectious disease service and intensive care unit of the University Hospital of Lausanne, who managed COVID-19 patients. We thank all general practitioners and their medical assistants who participated in the primary care study. We thank Hélène Donnet and Marie-Josée Vez for helping in sample collection at the emergency department. We are grateful to Martin Delaloye who helped us with sample storage and triage. We thank Marie-Anne Page and the team of molecular microbiology for their support in running SARS-CoV-2 PCR.

Funding: None.Competing Interests: None declared.Ethical Approval: Not required.