While the COVID-19 pandemic shows no signs of subsiding, the approaching winter also paves way for the flu season. However, according to a study by Yale University, the prevalence of another viral infection may offer protection from influenza—the common cold virus.
The authors state that the Rhinovirus—a known cause of common cold—can inhibit the flu virus from invading the airways by triggering the body's antiviral defense mechanism. This could explain the H1N1 swine flu pandemic's mysterious inactivity in Europe when cases were expected to spike during the fall, a time when common cold is widespread.
A Tango Between Common Cold and Influenza
For the study, the researchers examined three years' worth of clinical data of over 13,000 patients who were treated at the Yale New Haven Hospital for exhibiting symptoms of respiratory infections. The scientists made an astounding discovery. They found that even during months where both the pathogens were active, when the common cold virus was present, the flu virus was absent.
Dr. Ellen Foxman, senior author of the study, said in a statement, "When we looked at the data, it became clear that very few people had both viruses at the same time." In order to test the interaction between the influenza virus and rhinovirus, the authors designed a human airway tissue from specialized stem cells from which epithelial cells arose.
Activating the Body's Immune Response
Epithelial cells are cells that form the lining of the airways of the lung and are the principal target of infections for respiratory viruses. The scientists found that following the tissue's exposure to the rhinovirus, the influenza virus was incapable of causing infection in the tissue. "The antiviral defenses were already turned on before the flu virus arrived," Foxman said.
She explained that the presence of rhinovirus activated the production of interferon, a signaling protein that initiates an antiviral response, and is a component of the body's early immune system response to invading pathogens. "The effect lasted for at least five days," Foxman stated.
Can Common Cold Virus Offer Protection Against COVID-19?
The SARS-CoV-2, which causes COVID-19, is also a virus that attacks the respiratory system. So the question is, can Rhinovirus infection provide protection against COVID-19? Foxman answered that it is still not known whether the yearly seasonal spread of common cold could have a similar effect on the rate of infection among those exposed to the novel coronavirus.
"It is impossible to predict how two viruses will interact without doing the research," she expressed. However, Foxman said that her team has begun investigating whether the introduction of the common cold virus prior to the infection by the coronavirus provides a similar kind of protection.