The most frequent cause of common colds, rhinovirus, may be able to prevent influenza by jumpstarting the body’s antiviral defenses, according to research published in The Lancet Microbe. The findings may reveal a surprising ally in the battle to minimize flu-related hospitalizations during the upcoming flu season.

Investigators at Yale studied 3 years of clinical data from more than 13,000 patients with symptoms of respiratory infection. They found that even during months when both rhinovirus and influenza were active, if the common cold virus was present then the flu virus was not.

“When we looked at the data, it became clear that very few people had both viruses at the same time,” said researcher Ellen Foxman, MD, PhD, in a press release.

These results may also explain findings during the 2009 H1N1 swine flu pandemic, when the expected surge in swine flu cases was never seen in Europe during the fall as the common cold became more widespread. Foxman added, however, that researchers do not know whether the annual seasonal spread of rhinovirus will have a similar impact on infection rates of those exposed to coronavirus disease 2019 (COVID-19).

“It is impossible to predict how 2 viruses will interact without doing the research,” she said in the release.

In order to test how the rhinovirus and influenza viruses interact, investigators created human airway tissue from stem cells that give rise to epithelial cells, which are a key target of respiratory viruses. They found that after the tissue had been exposed to rhinovirus, the influenza virus was unable to infect the tissue.

The presence of rhinovirus triggered production of the antiviral agent interferon, which is part of the early immune system response to invasive pathogens.

“The antiviral defenses were already turned on before the flu virus arrived,” Foxman said.

She added that the effect lasted for at least 5 days, and the lab has started studying whether introduction of the cold virus before infection by COVID-19 offers a similar type of protection.

REFERENCE
Common cold combats influenza [news release]. Yale; September 4, 2020. https://news.yale.edu/2020/09/04/common-cold-combats-influenza. Accessed September 10, 2020.