We need to reevaluate our current understanding and expectations of common viruses.
Dr John-Sebastian Eden
The study documents a major shift in the epidemiology of RSV following the emergence of SARS-CoV-2, the virus responsible for COVID-19.
Much like contact tracers working to map the spread of the virus in a community, the researchers mapped the circulation of viruses at the genetic level – called “genetic epidemiology”.
The researchers genetically sequenced hundreds of RSV-positive samples collected before and after the COVID-19 pandemic and used this data to create a genetic “family tree” – tracing the lineage of each viral strain.
Prior to COVID-19, two major RSV subtypes (A and B) co-circulated at similar levels.
From late 2020 to early 2021 during epidemic times, this changed dramatically. The RSV-A subtype was found to be the dominant strain – accounting for over 95% of cases in all states. The RSV-B had practically disappeared.
“We found instead that there were two new strains of RSV, both RSV-A subtypes, and they were distinct in geographic origin,” Dr Eden said.
“One was responsible for cases in NSW, ACT and VIC, and another responsible for cases in WA.”
Dr Eden said the COVID-19 pandemic has introduced unique circumstances shaping the genetic landscape of the virus in Australia and around the world, with significant consequences for how the genetic diversity of RSV will be restored.
As part of the evolutionary process, viruses naturally accumulate small genetic changes, just enough to make them distinct, but also possible to trace the changes back to their viral “parent”, similar to a genetic family tree. These strains coexist in the environment and are the source of genetic diversity.
The researchers found that the genetic diversity of RSV-A and RSV-B was extremely low, but will likely be restored as international borders continue to open.
This study was an international collaboration, including the Sydney Institute for Infectious Diseases and the Westmead Institute for Medical Research (Dr John-Sebastian Eden), Dr Jen Kok and Professor Dominic Dwyer, PathWest Laboratories in Perth (Professor David Smith), the WHO Collaborating Influenza Reference and Research Center at the Doherty Institute (Professor Ian Barr) and the University of Hong Kong (Dr Vijaykrishna Dhanasekaran).