Austrian study reveals important features of the virus: The analysis of infection clusters and widespread events in Austria formed the basis for obtaining general information about the transmission properties between people and the mutation of the virus in patients. Photo credit: Andreas Bergthaler’s Group / CeMM
Learning from previous SARS-CoV-2 outbreaks for future pandemic control.
By doing COVID-19 In a pandemic, 57 million people worldwide are already infected. In the search for vaccines and therapies, a thorough understanding of the virus, its mutations and mechanisms of transmission is crucial. 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 the epidemiological data in Austria and the state-of-the-art sequencing of the virus genome have gained unparalleled knowledge about the mutation behavior and transmission of the virus SARS-CoV-2 Virus.
The “Mutational Dynamics of SARS-CoV-2 in Austria” project was launched at the end of March by CeMM in close cooperation with the Medical University of Vienna. Together with the Austrian Agency for Health and Food Safety (AGES) and in cooperation with numerous universities and hospitals across Austria, scientists are working to draw a more precise picture of the virus mutations and transmissions that occur through the genome sequencing of SARS-CoV-. 2 viruses. Under the direction of CeMM main researchers Andreas Bergthaler and Christoph Bock, 750 samples from important SARS-CoV-2 infection clusters in Austria such as the tourist city of Ischgl and Vienna were phylogenetically and epidemiologically reconstructed and their role in the spread of the transcontinental virus was analyzed. The results also provide important information on the transmission and development of mutations in the SARS-CoV-2 virus.
The analysis of epidemiologically validated chains of infection in Austrian superspreading events showed that a relatively large average dose of 1000 infectious virus particles is transmitted. Photo credit: CeMM
Mutation analyzes revealed correlations between clusters
Based on epidemiological data, the scientists used mutation analysis to reconstruct a SARS-CoV-2 cluster from 76 cases and uncover a cryptic connection between two epidemiological clusters. “This example shows how contact tracing and virus mutation analysis together represent a strong pillar of modern pandemic control,” says project manager Andreas Bergthaler. Franz Allerberger, head of the Public Health department at AGES and co-author of the study, agrees: “The modern techniques of virus genome sequencing support epidemiological contact tracking and offer high-resolution insights into the ongoing pandemic.”
Researchers watch the development of new mutations
A special feature of the study is that a chain of eight successive transmissions was analyzed. “The chain of transmission began with a returnee from Italy. Within 24 days, the SARS-CoV-2 virus spread in the greater Vienna area via public and social events in closed rooms, ”said the authors of the CeMM study Alexandra Popa and Jakob-Wendelin Genger. The precise breakdown of the chain of transmission enabled the scientists to closely monitor the development of a new mutation in SARS-CoV-2. “Thanks to excellent epidemiological and in-depth data on virus sequencing, we were able to follow how the SARS-CoV-2 virus mutated in one individual and was then transmitted to others,” explains Andreas Bergthaler. In addition, the scientists observed the mutation behavior of the virus in 31 patients during the course of the disease. This may be helpful in the future to assess whether treatments affect the mutational properties of the virus.
Last author Andreas Bergthaler with first authors Alexandra Popa and Jakob-Wendelin Genger. Photo 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 the next. Overall, these values are considerably higher than for other viruses such as HIV or noroviruses. Andreas Bergthaler adds: “Occasionally, however, we also found infected people who apparently came into contact with fewer virus particles and still became infected. We suspect that parameters such as the use of protective measures, the transmission route or the immune system could play a decisive role here. “These results raise important new questions and hypotheses. Reducing the viral load of infected people through a combination of measures such as mouth and nose protection, physical removal and adequate indoor air exchange could play a key role in both preventing the virus from spreading and possibly even influencing the course of the disease.
The current study, based on data collected in the early stages of the SARS-CoV-2 pandemic in Spring 2020, provides important insights into the fundamental dynamics of SARS-CoV-2 mutations in patients and during transmission events. These results support other ongoing research projects aimed at better understanding and controlling the pandemic.
Find out more about the project: www.sarscov2-austria.org
Reference: “The genomic epidemiology of super-spreading events shows the mutation dynamics and the transmission properties of SARS-CoV-2” by Alexandra Popa, Genob Jakob-Wendelin, 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, November 23, 2020, Scientific translational medicine.
DOI: 10.1126 / scitranslmed.abe2555
Funding: The project is co-financed by a COVID Rapid Response grant from the Vienna Science and Technology Fund (WWTF) as well as contributions in kind from CeMM, the Austrian Academy of Sciences, the Medical University of Vienna and their respective partners.
