Obesity may impact flu transmission, severity of illness

Obesity may play a role in how flu spreads, according to a new study

A new study suggests that obese adults infected with flu shed the virus for a longer time. This makes them more likely to spread the infection. The study has been published in the Journal of Infectious Diseases.

It is a well known fact that obesity increases a person’s risk for severe complications from influenza, including hospitalization and even death.

“This is the first real evidence that obesity might impact more than just disease severity,” said senior study author Aubree Gordon, MPH, PhD, of the University of Michigan School of Public Health. “It might directly impact transmission as well.”

Further research is now underway to help determine if the flu virus shed for longer periods by obese individuals is indeed infectious

Researchers analyzed data collected from approximately 1,800 people in 320 households in Managua, Nicaragua, and corroborated the effect of obesity on the duration of viral shedding over three influenza seasons from 2015 to 2017. Obese adults with flu symptoms and laboratory-confirmed influenza shed influenza A virus for 42 percent longer than adults with flu who were not obese. The obese individuals infected with flu who were only mildly ill or had no symptoms shed influenza A virus for 104 percent longer than non-obese adults with flu.

Nose and throat samples were tested for determination of duration of viral shedding. The tests detected the presence of influenza virus RNA. Further research is now underway to help determine if the flu virus shed for longer periods by obese individuals is indeed infectious, Dr. Gordon said.

The differences seen in the duration of viral shedding were limited to influenza A viruses which causes epidemics in humans. The last such pandemic was in 2009 due to influenza A virus H1N1. Researchers found no association with obesity and the duration of shedding of influenza B virus, which typically causes less serious illness in adults and does not cause pandemics. Obesity also did not appear to impact the duration of viral shedding among children included in the study.

Obesity can alter the body’s immune response and lead to chronic inflammation, which increases with age, in addition to making breathing more difficult and increasing the need for oxygen. These factors may help explain how obesity could affect influenza risk, severity, and transmission potential, the study authors noted.

With rates of obesity rising rapidly around the world including India, the new findings, if supported by future studies, suggest that obesity may play an increasingly important role in flu transmission.