We need to re-evaluate our current understanding and expectations of a common virus.
Dr. John-Sebastian Eden
The study documents a major change in the epidemiology of RSV following the emergence of SARS-CoV-2, the virus responsible for COVID-19.
Unlike contact tracers that work to map virus spread in a community, the researchers mapped the circulation of viruses at the genetic level – a process called ‘genetic epidemiology’.
Researchers genetically sequenced hundreds of RSV-positive samples collected before and after the COVID-19 pandemic and used this data to build a genetic ‘family tree’ – tracing the lineage of each virus strain.
Before COVID-19, the two major RSV subtypes (A and B) co-circulated at similar levels.
During the outbreak period in late 2020 to early 2021, this changed dramatically. The RSV-A subtype was found to be the predominant strain—in more than 95 percent of cases in all states. RSV-B Everything had disappeared.
“We found instead that there were two new RSV strains, both RSV-A subtypes, and they were distinct in their geographic origin,” Dr. Eden said.
“One was responsible for cases in NSW, ACT and VIC, and the other was responsible for cases in WA.”
Eden said the COVID-19 pandemic had introduced unique circumstances shaping the genetic landscape of the virus in Australia and globally, with important consequences for how the genetic diversity of RSV would be restored.
As part of the evolutionary process, viruses naturally accumulate small genetic changes, enough to make them distinct, but also trace changes to their virus ‘parents’, similar to a genetic family tree possible. These strains coexist in the environment and this is what causes the genetic diversity.
The researchers found that the genetic diversity for RSV-A and RSV-B was extremely low, but will likely be restored as international borders continue to open.
The study was an international collaboration, with the Sydney Institute for Infectious Diseases and the Westmead Institute for Medical Research (Dr John-Sebastian Eden), Dr Jan Kok and Professor Dominic Dwyer, Pathwest Laboratories in Perth (Professor David Smith), collaborating with WHO . The Center for Reference and Research on Influenza at the Doherty Institute (Professor Ian Barr), and the University of Hong Kong (Dr. Vijayakrishna Dhanasekaran).