Since January, when the World Health Organisation (WHO) declared the new coronavirus outbreak a global public health emergency, international experts have kept on researching the virus. The main goal is to learn enough about SARS-CoV-2 to allow specialists to develop the most effective preventive and containment strategies. While many unknowns remain, research about the new coronavirus has been progressing fast.
One of the most recent studies – conducted by researchers from the Bundeswehr Institute of Microbiology in Munich, the Klinikum München-Schwabing, Charité Universitätsmedizin Berlin, and University Hospital LMU Munich, all in Germany – claims to have found out when the virus is at its most infectious.
The new study has not yet been published in a peer-reviewed journal, . However, its authors have made a preprint of the research paper. The paper’s first author is Dr Roman Wölfel, from the Bundeswehr Institute of Microbiology.
To find out how likely the virus was to spread at different stages of an infection, and through what mediums, the researchers analysed various samples that they collected from nine individuals who had contracted SARS-CoV-2.
These were all people who had attended a hospital in Munich for diagnostics and treatment, and they all experienced mild symptoms. All of these individuals were young to middle-aged adults who had no significant underlying health conditions.
The researchers analysed samples of saliva and mucus, as well as blood, urine, and stool samples collected at various stages of the infection. They tested each of them to see if the virus was present, and if it had the ability to infect further. Samples from the patients’ throats revealed that the virus was most infectious during the first week after the person had contracted it. This was the case with 16.66% of throat swabs and 83.33% sputum (saliva and mucus) samples.
The researchers were unable to isolate the virus in samples that they collected after the 8th day from a person’s exposure to the virus. While blood and urine samples did not present any virus traces, stool samples did yield viral RNA.
However, the researchers were unable to create a viral culture from the virus RNA present in stool, which suggests that this may be an unlikely source of infection. “The prolonged viral shedding in sputum is relevant not only for hospital infection control but also for discharge management,” the researchers write.
Based on their findings, they suggest that going forward, medical professionals may be able to avoid hospital bed shortages by discharging people from the hospital early on and advising self-isolation.
They note that: “In a situation characterised by limited capacity of hospital beds in infectious diseases wards, there is pressure for early discharge following treatment. Based on the present findings, early discharge with ensuing home isolation could be chosen for patients who are beyond day 10 of symptoms (…)”
Abstract
Background: In coronavirus disease 2019 (COVID-19), current case definitions presume mainly lower respiratory tract infection. However, cases seen outside the epicenter of the epidemic may differ in their overall clinical appearance due to more sensitive case finding.
Methods: We studied viral load courses by RT-PCR in oro- and nasopharyngeal swabs, sputum, stool, blood, and urine in nine hospitalized cases. Infectious virus was detected by cell culture. Active replication was demonstrated by analysis of viral subgenomic replicative intermediates. Serology including neutralization testing was done to characterize immune response.
Results: Seven cases had upper respiratory tract disease. Lower respiratory tract symptoms seen in two cases were limited. Clinical sensitivity of RT-PCR on swabs taken on days 1-5 of symptoms was 100%, with no differences comparing swab and sputum samples taken simultaneously. Average viral load was 6.76x10E5 copies per swab during the first 5 days. Live virus isolates were obtained from swabs during the first week of illness. Proof of active viral replication in upper respiratory tract tissues was obtained by detection of subgenomic viral RNA. Shedding of viral RNA from sputum outlasted the end of symptoms. Seroconversion occurred after about one week.
Conclusions: The present study shows that COVID-19 can often present as a common cold-like illness. SARS-CoV-2 can actively replicate in the upper respiratory tract, and is shed for a prolonged time after symptoms end, including in stool. These findings suggest adjustments of current case definitions and re-evaluation of the prospects of outbreak containment.
Authors
Roman Woelfel, Victor Max Corman, Wolfgang Guggemos, Michael Seilmaier, Sabine Zange, Marcel A Mueller, Daniela Niemeyer Patrick Vollmar, Camilla Rothe, Michael Hoelscher, Tobias Bleicker, Sebastian Bruenink, Julia Schneider, Rosina Ehmann, Katrin Zwirglmaier, Christian Drosten, Cemens Wendtner
[link url="https://www.medicalnewstoday.com/articles/new-coronavirus-may-be-most-infectious-during-1st-week#Findings-may-have-impact-on-care-strategy"]Medical News Today material[/link]
[link url="https://www.medrxiv.org/content/10.1101/2020.03.05.20030502v1"]MedRXiv abstract[/link]