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An Austrian study reveals important characteristics of the virus: the analysis of infection clusters and super spread events in Austria laid the foundation for obtaining general information on the properties of transmission between people and the mutation of the virus in patients. Credit: Andreas Bergthaler’s Group / CeMM
Learn from past SARS-CoV-2 outbreaks for future pandemic control.
In COVID-19 pandemic, 57 million people have already been infected around the world. A precise understanding of the virus, its mutations and transmission mechanisms is essential in the search for vaccines and therapies. A recent study by the research group of Principal Investigator Andreas Bergthaler at the CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, in the renowned journal Science Translational Medicine, makes an important contribution to this. The high quality of epidemiological data in Austria, together with the state of the art of virus genome sequencing, has supported unprecedented insights into the behavior of the mutation and transmission of the SARS-CoV-2 virus.
The “Mutational dynamics of SARS-CoV-2 in Austria” project was launched by the CeMM in close cooperation with the Medical University of Vienna at the end of March. Together with the Austrian Agency for Health and Food Safety (AGES) and in collaboration with numerous universities and hospitals across Austria, scientists are working to draw a more precise picture of the mutations and transmissions of the virus that occur through the genome sequencing of SARS-CoV- 2 viruses. Under the guidance of CeMM Principal Investigators Andreas Bergthaler and Christoph Bock, 750 samples from important SARS-CoV-2 infection clusters in Austria such as the tourist cities of Ischgl and Vienna were phylogenetically and epidemiologically reconstructed and their role analyzed. in the transcontinental spread of the virus. The findings also provide important information on the transmission and development of mutations in the SARS-CoV-2 virus.
Analysis of epidemiologically validated infection chains in Austrian superspansion events found that a relatively high average dose of 1000 infectious viral particles is transmitted. Credit: CeMM
Mutation analyzes revealed correlations between clusters
Based on epidemiological data, the scientists used mutation analysis to reconstruct a SARS-CoV-2 cluster consisting of 76 cases and to discover a cryptic link between two epidemiological clusters. ‘This example illustrates how contact tracing and virus mutation analysis together provide a strong pillar of modern pandemic control,’ says project leader Andreas Bergthaler. Franz Allerberger, head of AGES’s public health division and co-author of the study, agrees: “Modern virus genome sequencing techniques support epidemiological contact tracing and offer high-resolution insights into the ongoing pandemic.”
Researchers observe the development of new mutations
A special feature of the study is that a chain of eight consecutive transmissions was analyzed. “The chain of transmission began with a returnee from Italy. Within 24 days, the SARS-CoV-2 virus spread to the greater Vienna region through public and social events in closed rooms, ”say CeMM study authors Alexandra Popa and Jakob-Wendelin Genger. Precise breaking of the transmission chain allowed scientists to closely observe the development of a new mutation of SARS-CoV-2. “Thanks to the excellent epidemiological data and our deep virus sequencing data, we were able to follow how the SARS-CoV-2 virus mutated in one individual and was then passed on to others,” explains Andreas Bergthaler. Furthermore, the scientists observed the mutation behavior of the virus during the course of the disease in 31 patients. This could help in the future to assess whether treatments affect the mutation characteristics of the virus.
The latest author Andreas Bergthaler with the first authors Alexandra Popa and Jakob-Wendelin Genger. Credit: Klaus Pichler / CeMM
An average of 1,000 virus particles are transmitted during an infection
The results of the current analyzes also show that an average of 1000 infectious virus particles are transmitted from one infected person to another. Overall, these values are considerably higher than those of other viruses such as HIV or noroviruses. Andreas Bergthaler adds: “However, we also occasionally found infected people who apparently came into contact with fewer viral particles and were still infected. We suspect that parameters such as the application of protective measures, the route of transmission or the immune system may play a decisive role here. “These findings raise important new questions and hypotheses. Reduce the viral load of infected individuals by a combination of measures such as mouth-nose protection, physical distance and adequate internal air exchange could play a key role both in preventing the spread of the virus and possibly also influencing the course of the disease.
The current study, based on data collected during the initial phase of the SARS-CoV-2 pandemic in spring 2020, provides important insights into the fundamental dynamics of SARS-CoV-2 mutations within patients and during transmission events. . These findings support other ongoing research projects aimed at better understanding and controlling the pandemic.
Find out more about the project: www.sarscov2-austria.org
Reference: “Genomic Epidemiology of Super Diffusion Events Reveals Mutational Dynamics and Transmission Properties of SARS-CoV-2” by Alexandra Popa, Jakob-Wendelin Genger, Michael D. Nicholson, Thomas Penz, Daniela Schmid, Stephan W. Aberle , Benedikt Agerer, Alexander Lercher, Lukas Endler, Henrique Colaço, Mark Smyth, Michael Schuster, Miguel L. Grau, Francisco Martínez-Jiménez, Oriol Pich, Wegene Borena, Erich Pawelka, Zsofia Keszei, Martin Senekowitsch, Jan Laine, Judith H. Aberle, Monika Redlberger- Fritz, Mario Karolyi, Alexander Zoufaly, Sabine Maritschnik, Martin Borkovec, Peter Hufnagl, Manfred Nairz, Günter Weiss, Michael T. Wolfinger, Dorothee von Laer, Giulio Superti-Furga, Nuria Lopez-Bigas, Elisabeth Puchhammer- Stöckl, Franz Allerberger, Franziska Michor, Christoph Bock and Andreas Bergthaler, 23 November 2020, Scientific translational medicine.
DOI: 10.1126 / scitranslmed.abe2555
Funding: The project is co-funded by a COVID-Rapid Response grant from the Vienna Science and Technology Fund (WWTF) and in-kind contributions from the CeMM, the Austrian Academy of Sciences, the Medical University of Vienna and their respective partners.
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