The novel coronavirus responsible for COVID-19 could become nothing more than an annoying seasonal cold within the next decade.
A new study, carried out by researchers at the University of Utah and published in the journal Viruses, used mathematical models to predict the possible future of the virus.
Models factored in lessons learnt from the COVID-19 pandemic on how the body's immunity changes and adapts over time.
The findings suggest that changes in the severity of the disease could be driven by "adaptations of our immune response" rather than changes in the virus itself.
Senior author, professor of mathematics and biological sciences Fred Adler, says the findings show a "possible future that has not yet been fully addressed".
"Over the next decade, the severity of COVID-19 may decrease as populations collectively develop immunity."
Although SARS-CoV-2, the coronavirus responsible for COVID-19, is the most well-known, there are a number of seasonal coronaviruses that circulate and cause a less severe illness, the study explains.
"Some evidence indicates that one of these cold-causing relatives might have once been severe, giving rise to the 'Russian flu' pandemic in the late 19th century. "
Researchers wanted to figure out whether, like the Russian flu, the severity of COVID-19 would lessen over time.
They ran several mathematical models which counted for scenarios, including:
- there is likely a dose-response between virus exposure and disease severity
- a person exposed to a small dose of virus will likely get a mild case of COVID-19 and shed small amounts of virus
- adults exposed to a large dose of virus are more likely to have severe disease and shed more virus
- masking and social distancing decrease the viral dose.
They also accounted for people who may have levels of immunity through vaccination or by having caught COVID-19 before.
The models all resulted in a "situation where an increasing proportion of the population will become predisposed for a mild disease over the long term" meaning people will be more likely to experience a less severe illness.
"In the beginning of the pandemic, no one had seen the virus before," Dr Adler explains. "Our immune system was not prepared."
Modelling shows as more adults become partially immune through vaccination or prior infection, severe symptoms will "all but disappear" over the next decade.
The models didn't account for every potential influence on disease trajectory, for example, new virus variants taking hold in the community.
"Our next step is comparing our model predictions with the most current disease data to assess which way the pandemic is going as it is happening," Dr Adler says.
"Do things look like they're heading in a bad or good direction? Is the proportion of mild cases increasing? Knowing that might affect decisions we make as a society."
So far globally there have been 166 million cases of COVID-19 and 3.44 million deaths. Both are vast undercounts, the World Health Organization said this week.