Adults Who Are Obese and Have Influenza May Be Contagious Longer

Woman with the flu

New Research from Aubree Gordon

People who are obese are at an increased risk of serious diseases and health conditions, with obesity increasing the risk of severe complications and death from influenza virus infections, especially in elderly individuals.

A new study suggests that obesity may also play an important role in influenza transmission, says lead researcher Aubree Gordon, assistant professor of Epidemiology at the University of Michigan School of Public Health, who discussed her research.

Gordon, whose research focuses on infectious disease epidemiology and global health, has been working on the epidemiologic features and transmission of influenza in Nicaraguan households. Her team looked at data from more than 1,800 individuals in 320 households in Managua, Nicaragua, from 2015 to 2017. They focused on 'viral shedding,' or how long influenza virus can be found in people's mucous.

Q: What were the key findings of your study?

Gordon: What we've found in this study was that obese adults shed influenza A virus for significantly longer than nonobese adults. Overall, they shed virus for 42 percent longer. We looked at individuals that were either asymptomatic—meaning that they had no symptoms—or they were paucisymptomatic—they had one minor symptom maybe a bit of headache, nothing major. Those obese adults shed influenza virus A for about twice as long as nonobese adults with the same symptoms.

Q: Why is this significant?

Gordon: The significance of this finding is that previously obesity has been shown to be a risk factor for severe influenza. But this indicates that obesity may also affect influenza transmission. The potential impact for people around that individual is that if a person is shedding influenza virus longer, they're probably infectious for longer. And so that will increase the probability that the people they come into contact with could get the virus.

Obesity is a huge problem worldwide. We really have a pandemic of obesity going on. We already know that obesity affects the burden of chronic diseases and severity of several infectious diseases, but this indicates that it may also affect transmission so it may increase the rates of infectious diseases.

Q: Are there any practical applications to this information?

Gordon: Obese individuals are already a target population for vaccines and antivirals but certainly encouraging individuals to get vaccinated, particularly if they are obese or have other risk factors, is important. And then getting this information out to physicians might make it more likely that they will test their patients for influenza and prescribe antivirals.

The study was funded by the National Institute of Allergy and Infectious Diseases and the Fogarty International Center, both of the National Institutes of Health.