How did Covid-19 make drastic changes to the ‘winter virus’?

One of the first studies to document the impact of COVID-19 on viruses already in Australia revealed how the epidemic was responsible for dramatically changing the incidence and genetics of respiratory syncytial virus (RSV) in the country.

RSV is a common virus that generally causes mild symptoms similar to those of a cold, and the infection can be serious, especially in infants and the elderly.

Researchers say the epidemic has disrupted the seasonal pattern of RSV, a key member of a group of regular “winter viruses.” For the first time ever, during 2020, the winter RSV epidemic was absent due to COVID-19 travel restrictions and infection control measures.

However, RSV was one of the first major respiratory pathogens to re-emerge after COVID-19.

Posted in Nature CommunicationsAnd the Researchers have genetically sequenced (generated and mapped genetic fingerprints of the virus) to the off-season RSV outbreak during the summer of 2020-21 on both sides of the country.

The outbreak coincided with the easing of measures to control Covid-19.

The surprising discovery was the significant collapse of RSV strains already known before COVID-19, and the emergence of new RSV strains that have dominated every outbreak in Western Australia, New South Wales and the Australian Capital Territory.

Importantly, the researchers then tracked the scattering of viruses from each outbreak in Victoria, which led to another major RSV outbreak.

“Our genetic studies have shown that most previous RSV strains have become extinct and only one genetic strain has survived in each of the closures,” said lead researcher Dr. From the Sydney Institute of Infectious Diseases, School of Medicine and Health, and is based at the Westmead Institute for Medical Research.

“We need to re-evaluate our current understanding and expectations of common viruses, including influenza, and change our approach to how we manage them.”

The study also raises important questions about how quickly the spread and evolution of respiratory syncytial virus (RSV) can help re-emergence of other viruses including influenza.

The range of influenza strains circulating before and after COVID-19 has changed a lot, resulting in challenges in how we choose the composition and timing of our annual vaccines. For example, the flu season in Australia started much earlier than in previous years.” Dr. Eden said

There is currently no RSV vaccine, but it is a major focus of vaccine and treatment development.

“We need to be vigilant – some viruses may be nearly gone, but it is likely that they will recover in the near future, perhaps at extraordinary times and with a stronger impact,” said Dr. Eden.

“We need to be prepared for a significant spread of RSV outside of normal seasonal periods and to be prepared for our health systems.”

The outlook of the virus is changing

The study documents a major shift in the epidemiology of RSV after the emergence of SARS-CoV-2, the virus responsible for COVID-19.

In contrast to contact tracing tools that map the spread of a virus in a community, researchers have mapped the spread of viruses at the genetic level – called “genomic epidemiology”.

Researchers have 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) circulated at similar levels.

During late 2020 to early 2021 during periods of outbreak, this changed dramatically. The RSV-A subtype was found to be the dominant strain — making up more than 95 percent of cases in all states. RSV-B is completely gone.

“We instead found two new strains of RSV, both RSV-A subtypes, that were different in their geographic origin,” said Dr. Eden.

“One was responsible for cases in NSW, ACT and VIC, and the other was responsible for cases in Washington.”

Dr Eden said the COVID-19 pandemic has introduced unique conditions to shape the genetic landscape of the virus in Australia, and globally, with important consequences for how RSV genetic diversity can be restored.

As part of the evolutionary process, viruses naturally accumulate small genetic changes, just enough to make them distinct, but it is also possible to trace changes back to their viral ‘mother’, similar to a genetic family tree. These strains coexist in the environment and this is what causes genetic diversity.

The researchers found that the genetic diversity of RSV-A and RSV-B was very low but likely to be restored as international borders continue to open.

This study was an international collaboration, including the Sydney Institute of Infectious DiseasesAnd the the Westmead Institute for Medical Research (Dr John Sebastian Eden), Dr Jane Cook and Professor Dominic Dwyer), PathWest Laboratories in Perth (Professor David Smith), the WHO Collaborating Center for Reference and Research on Influenza at the Doherty Institute in Melbourne (Professor Ian Barr), and University of Hong Kong (Dr. Vijaykrishna Danasekaran).

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2022-05-30 22:18:45

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