Having Influenza May Keep the Common
Cold Away

Jennifer Garcia

December 16, 2019

Interaction between cold and influenza viruses can actually diminish the prevalence of the common cold during peak flu season thanks to adaptive immunity, according to a study published online today in the Proceedings of the National Academy of Sciences.

Sema Nickbakhsh, PhD, a postdoctoral research associate from the MRC-University of Glasgow Centre for Virus Research, United Kingdom, and colleagues analyzed data from 44,230 cases of respiratory illness between 2005 and 2013. They tested all cases for 11 respiratory virus groups and included in their analysis alternative drivers of infection frequency, including age, sex, and disease severity.

Using bespoke analysis and mathematical simulations to assess the propensity of a given virus to co-infect with another virus at both the population and individual host levels, the researchers confirmed a negative interaction between seasonal influenza A virus (IAV) and rhinovirus (RV), the virus which causes the common cold (odds ratio, 0.27; P < .001).

The study authors posit that "this negative interaction may be driven by virus competition for susceptible cells, for example as a consequence of influenza-induced destruction of cell surface receptors and/or cell death, or as a consequence of virus-induced innate immune responses, such as the secretion of interferon, which can cause noninfected neighboring cells to adopt a protective antiviral state."

The researchers go on to suggest this "transient immune-mediated cross-protection" may result in alterations in viral transmission such that recent infection with IAV would leave the host less susceptible to subsequent viral infection with RV.

They say their simulations show this "refractory period" could lead to a significant decline in common colds. As an example, they found that a refractory period of 2 days led to a 23% decrease in the incidence of cold-like virus during peak influenza virus activity, whereas a 7-day refractory period resulted in a 61% decrease.

The researchers acknowledge virus–virus interactions are dependent on multiple host and environmental factors and that clinical symptoms of infection with IAV and RV can be quite variable at the population and individual host levels.

"Our findings imply that the incidence of influenza infections is interlinked with the incidence of noninfluenza viral infections with implications for the improved design of disease forecasting models and the evaluation of disease control interventions," the authors conclude.

The authors have disclosed no relevant financial relationships.

Proc Natl Acad Sci USA. Published online December 16, 2019. Full text

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