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Tuesday, February 11, 2025

Study Shows The Rhinovirus, The Common Cold, Should Be Taken More Seriously

Although studies have shown that the Rhinovirus can come in up to atleast 150 different variants, and although rhinovirus is the most common cause of upper respiratory infections, relatively little is known about its evolution and spread.

By Aaron Allen, The Seattle Medium

According to new research from the University of Washington School of Medicine in Seattle, the most common cause of the common cold is the rhinovirus, because it increases its chances of infecting someone who lacks immunity by simultaneously circulating many versions of itself.

“With viruses like SARS-CoV-2 or influenza, one variant will dominate for a while, then another takes over, and it, in turn, is replaced by another,” said Dr. Alex Greninger, professor of laboratory medicine and pathology, who led the study. “Rhinovirus, on the other hand, appears to flood the zone with many discrete variants circulating in the community at the same time. It’s a way to overcome your defenses with sheer numbers.”

Although rhinovirus is the most common cause of upper respiratory infections, relatively little is known about its evolution and spread. The University of Washington researchers sought to change that by analyzing nasal swabs collected in the Seattle area during the COVID-19 pandemic. They focused on two specific periods to understand how different public health measures influenced the circulation of rhinovirus and other respiratory viruses:

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• Spring and summer of 2021: During this time, strict COVID-19 public health measures were in place, which slowed the spread of SARS-CoV-2 and nearly eliminated other respiratory infections, such as influenza and respiratory syncytial virus (RSV).

• Fall and winter of 2022: By this period, public health restrictions had been relaxed, leading to the resurgence of influenza and RSV, alongside continued cases of SARS-CoV-2.

The data from these periods revealed a surprising pattern. While public health measures effectively reduced the spread of many respiratory viruses in 2021, rhinovirus infections continued to circulate widely. This finding suggested that rhinovirus operates differently than other viruses, such as SARS-CoV-2, influenza, and RSV, which tend to be more affected by social distancing and mask-wearing.

“Imagine that even right now, you may have a mild respiratory illness, so a cold,” said Stephanie Goya, a postdoctoral research scientist in the Greninger lab. “During the COVID-19 outbreak, people were concerned about SARS-CoV-2, but they may have actually had rhinovirus. This is a virus that some general community physicians might not pay much attention to because, for many years, it was just seen as the common cold virus.”

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Goya noted the unique challenge presented by the persistence of rhinovirus during the pandemic.

“Basically, there were only two viruses spreading during the pandemic restrictions: SARS-CoV-2 and rhinovirus,” she said. “We were curious about what was happening: Was one rhinovirus species dominating, or was a new, emergent variant causing these infections?”

When public health restrictions were relaxed in 2022, influenza, RSV, and SARS-CoV-2 reemerged, creating what became known as the “tripledemic.” During this period, rhinovirus remained widely prevalent, demonstrating its ability to circulate alongside other respiratory viruses, regardless of the public health environment.

To identify which viral variants were circulating during these two periods, the researchers sequenced over 1,000 RNA genomes of rhinoviruses from tens of thousands of swabs collected. These sequences provided genetic fingerprints, or genotypes, that allowed the researchers to determine which types of rhinovirus were circulating at any given time. The researchers then created “family trees” to map how different genotypes were related and evolved.

The study revealed that no single rhinovirus variant was dominant. Instead, 99 different genotypes were circulating in the region during the study periods. The analysis showed that many of these genotypes have been around for up to 40 years and have stable protein sequences. Researchers believe the virus’s success comes from the simultaneous presence of a variety of genotypes, rather than from new evolutionary changes. Since each genotype is recognized differently by the immune system, each spreads effectively at different times.

“Researchers have been discovering and describing rhinovirus variants for about 50 years,” said Goya. “So far, we’ve discovered around 160 to 170 variants, and we will likely find more as we continue to search.”

The study found that 66% of people whose swabs tested positive for rhinovirus reported symptoms such as sore throat, runny nose, and cough. Swabs from symptomatic individuals tended to have higher viral loads, but no specific rhinovirus species or genotype was found to cause more symptoms than others. The mix of circulating genotypes varied, with some being more prevalent at different times. Notably, genotypes that predominated in the first collection period were largely replaced by others in the second period.

When asked if certain populations are more susceptible to rhinovirus, Goya said, “There is no evidence that some populations are more susceptible than others. This virus can affect anyone at any time, many times.”

This may suggest that immunity developed in the population in 2021 influenced which genotypes could spread the following year. The study also found some changes in segments of the viral genome that affect the structure of the proteins that attach to cells in the nose and throat. These proteins are often important targets for antibodies and other immune responses.

“Because the structural changes are few, it might be possible to create a vaccine that generates an effective immune response to a large number of genotypes and, hopefully, prevent many common colds,” Goya said.

The persistence of rhinovirus, even under strict public health measures, underscores its unique adaptability and ability to evade immune defenses. Unlike other viruses, which often see one dominant strain at a time, rhinovirus operates on a model of diversity, with multiple genotypes circulating simultaneously. This strategy allows it to remain a constant presence in the community, often unnoticed due to its association with the common cold.

The findings from this study are particularly important in light of ongoing discussions about virus surveillance and vaccine development. As the research shows, rhinovirus is not just a benign virus that causes a runny nose or sore throat; it has a complex strategy for evading the immune system and maintaining its presence in human populations. Understanding this strategy could be key to developing more effective vaccines and treatments, not just for rhinovirus but for other respiratory viruses as well.

Studies like this are critical in educating the general public about the importance of taking all viruses seriously, even those that might seem as harmless as the common cold. Rhinovirus can still pose a threat, especially to those with underlying health conditions, the elderly, or the immunocompromised. The research underscores the need for continued vigilance in monitoring and understanding the full spectrum of respiratory viruses to better protect public health.

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