We need to re-evaluate our current understanding and expectations of common viruses.
Dr. John-Sebastian Eden
The study documents a significant change in the epidemiology of RSV after the onset of SARS-CoV-2, the virus responsible for COVID-19.
Unlike contact tracers that work 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 positive RSV samples collected before and after the COVID-19 pandemic and used that data to create a genetic “family tree,” tracing the lineage of each strain of virus.
Prior to COVID-19, two major subtypes of RSV (A and B) co-circulated at similar levels.
Between late 2020 and early 2021 during the outbreak periods, this changed drastically. The RSV-A subtype was found to be the dominant strain, accounting for more than 95 percent of cases in all states. The RSV-B was almost gone.
“Instead, we found that there were two new strains of RSV, both subtypes of RSV-A, and they were different in their geographical origin,” Dr. Eden said.
“One was responsible for the cases in NSW, ACT and VIC, and another was responsible for the cases in WA.”
Dr Eden said the COVID-19 pandemic had introduced unique circumstances that shaped the virus’s genetic landscape in Australia and around the world, with major implications for how RSV’s genetic diversity will be restored.
As part of the evolutionary process, viruses naturally accumulate small genetic changes, just enough to differentiate them, but it is also possible to trace the changes to their “father” of the virus, similar to a family tree. These strains coexist in the environment and is what causes genetic diversity.
The researchers found that genetic diversity for RSV-A and RSV-B was extremely low, but is likely to be restored as international borders continue to open.
This study was an international collaboration, which includes the Sydney Institute of Infectious Diseases and the Westmead Institute for Medical Research (Dr John-Sebastian Eden), Dr. Jen Kok and Professor Dominic Dwyer, PathWest Laboratories of Perth (Professor David Smith), WHO Collaborator. Influenza Reference and Research Center of the Doherty Institute (Professor Ian Barr) and the University of Hong Kong (Dr. Vijaykrishna Dhanasekaran).