New Insights into Cold-Flu Relationship May Help Better Predict Outbreaks: Public Health Watch

We’ve all heard the old axiom, “Feed a cold. Starve a fever.”

Now, a new analysis suggests we may need to rethink our view of these 2 age-old maladies with much in common.

In findings, published on December 16^th in the Proceedings of the National Academy of Sciences, investigators from the University of Glasgow in Scotland noted that people suffering from the common cold are less likely to be diagnosed with influenza virus, and vice versa. They believe this knowledge may help public health specialists better predict outcomes of the latter, which of course have been linked with significant disease burden and mortality.

“Our findings suggest that we need to do more coinfection studies in future research that involve respiratory viruses, including influenza,” coauthor Pablo Murcia, DVM, PhD, MSc, senior lecturer, University of Glasgow Centre for Virus Research, Institute of Infection, Immunity and Inflammation, told Contagion®. “Virologists have traditionally studied viruses in isolation—you study influenza or coronaviruses, for example. What our study shows is that viruses interact and in order to understand the mechanisms that explain the observed interactions we need to do more research. I think that increased awareness of the impact of virus-virus interactions in virus epidemiology and disease outcome would be beneficial, especially for infectious disease and public health specialists.”

For their research, Murcia and his team tested for 11 types of respiratory viruses in more than 44,000 samples taken from more than 36,000 people with acute respiratory illnesses. Of these samples, 35% tested positive for a virus, and 8% of those were infected with more than 1 virus.

Notably, according to Murcia, the most significant interaction was between influenza A viruses and rhinoviruses, aka the common cold. Computer modeling of these 2 viruses found that interactions between them inhibited infection with both. Overall, people with influenza A were about 70% less likely to also be infected with rhinovirus than those infected with other viruses.

The findings are particularly notable, given the threat posed by influenza A in Europe and elsewhere. According to new data from the European Centre for Disease Prevention and Control and the World Health Organization, initial virus detections for the 2019-20 season indicate cocirculation of influenza types A (71%) and B (29%) in the region. To date at least, the opposite has been the case here in the United States.

Unfortunately, as European epidemiologists note, increased circulation of influenza A could result in high mortality in elderly populations and a heavy burden on healthcare services.

“Epidemiological interactions between respiratory viruses have been postulated before,” Murcia said. “However, our study is the first one to provide strong statistical evidence on this issue. We were able to do that first because we had access to the diagnostic test results of tens of thousands of patients spanning multiple years and from a well-defined population here in Glasgow. A key aspect is that each patient that was tested, was screened for 11 different viruses in the same diagnostic lab. This very fact gave us a good picture of the virus status of each patient and also significant confidence about the reliability of our data.”

And it just may give epidemiologists a reliable way to predict influenza outbreaks in the future.