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What we still don't know about COVID-19 three years into the pandemic
We're stuck with COVID-19 and the virus that causes it, experts say. And while we have a better understanding of both than we did three years ago, there is still much we don't know.
Published
By David Aidone
Source: SBS News
Image: There is still much we don't know about COVID-19 and the virus that causes it, experts say. (SBS News / Leon Wang)
KEY POINTS
- The SARS-CoV-2 virus and the disease it causes, COVID-19, emerged three years ago.
- Experts say we now have a better understanding of the virus.
- But there are still things we don't know, like the virus' origin and how it could evolve.
We're more than three years into a pandemic in which we've seen international borders closed, people confined to just a few kilometres of their homes, and millions of deaths across the world.
And while restrictions might be a thing of the past, experts say some things remain unclear about what sparked them: the SARS-CoV-2 virus and the disease it causes, COVID-19.
What is clear is the virus "has a significant propensity to change", illustrated by the many variants that have emerged, and that we can now manage it more effectively, said Dr Paul Griffin, an infectious disease physician who works at Brisbane's Mater hospital, the University of Queensland, and research organisation the Nucleus Network.
"But it's not going to go away," Griffin said.
Some quarters of the scientific community have a view mutations will become milder over time, Griffin said, although he believes this is far from certain.
"We know the virus will continue to change, but what we don't know is what those changes will confer in terms of what the virus does," he said. "And that is why we have those discussions when new, concerning variants or subvariants emerge and work out what they're going to do."
When it comes to viral evolution, there's a general trend whereby a virus, when spreading in populations with strong immunity, will become better at evading the immune system at the expense of its transmissibility, said Professor Andrew Lloyd, an infectious diseases physician at the University of NSW's Kirby Institute.
"Often, but not always, would be the right thing to say," Lloyd said of the trend.
A summary of US intelligence, released in June, noted there was "no information" the Wuhan Institute of Virology — at the centre of the lab leak theory — was working on SARS-CoV-2. Source: AAP, AP / Koki Kataoka
Our immunity is built on exposure to the virus and COVID-19 vaccines, but we don't yet fully understand how long immunity lasts, according to the Department of Health, which says more research is needed to establish this.
Griffin agrees. He said COVID-19 vaccines work "tremendously well", providing protection against severe disease and, to a lesser degree, infection, but there was still room for improvement.
"Protection is certainly impacted by waning over time, and also by the immune evasion in new subvariants," Griffin said. "In terms of how long each vaccine will last, who gets what level of protection, how we assess who's protected and who's not, what the ideal interval for repeat vaccines is ... we still don't really know."
Researchers are also still learning about how the immune system protects us against the effects of COVID-19.
Lloyd said antibody response was well understood, but "another arm of the immune system", T cells, could play an important role.
"They're a bit like antibodies in that they specifically recognise individual targets - viruses in this case; so SARS-CoV-2-specific T cells contribute to protection and may be more important in the longer term against repeated infection," he said.
For some people, COVID-19 symptoms can persist for months or even years. This is known as long COVID, and we're yet to establish a comprehensive understanding of it, according to Professor Andrew Baillie, a professor of allied health at the University of Sydney who is also part of the Long-COVID Australia Collaboration — a group of researchers, health professionals and people with lived experience working on how to best respond to the complex health problem.
"We lack knowledge of the biological bases and of the best ways to treat it," he said.
Long COVID encompasses up to 200 different symptoms, including headaches and fatigue. We still don't have a comprehensive understanding of the condition. Credit: Adrian Swancar/Unsplash
That means we still don't know what its "essential features" are, Baillie said, which can make it difficult for a GP to provide someone with an early positive diagnosis.
"And we certainly don't have an explanatory diagnosis, which would explain the underlying process that causes all of this," he said. "We could say simply that it's COVID that causes all of this, but that doesn't help us with how to fix it."
The WHO provides a clinical case definition that is meant to help GPs in their day-to-day practice, Lloyd said. That's "less stringent" than a research case definition which, among other things, is what researchers would look at if developing a new intervention for long COVID.
"Many of the symptoms are very common individually in primary care unrelated to long COVID," Lloyd said. "So there's a bit of a problem there in getting a good, unified case definition."
And the origin of the virus? That also remains unclear, although a summary of United States intelligence released in June noted there was "no information" the Wuhan Institute of Virology (WIV) — at the centre of the lab leak theory — was working on SARS-CoV-2.
It also said there was "no direct evidence" that a "research-related incident" involving staff at the WIV "could have caused the COVID-19 pandemic".
Professor Dominic Dwyer, an infectious diseases physician at NSW Health Pathology who was also part of the WHO team that examined the origins of SARS-CoV-2, said most virologists believe the virus came from an animal.
"Coronaviruses (CoVs) that infected humans pre-COVID-19 have likely animal origins," Dwyer said in a Q&A with the Australian Science Media Centre on the virus' origins.
"For example, the ‘common cold’ CoVs, SARS and MERS. Coronaviruses of varying degrees of genetic relatedness can be readily detected in a wide range of land, air (and water) animals, and can jump species."
