New US research has found that obese individuals infected with influenza shed the virus for a longer period than those who are not obese, potentially increasing the opportunity for the infection to spread to others.
Carried out by researchers at the University of Michigan, the new study looked at data collected from around 1 800 people in 320 households in Managua, Nicaragua, to analyse the effect of obesity on the duration of viral shedding, which is when an infected person releases the virus, potentially passing it on to others.
The researchers looked at three influenza seasons from 2015 to 2017, and measured the duration of viral shedding using tests of nose and throat samples.
The results showed that obese adults with flu symptoms and confirmed influenza shed influenza A virus for 42% longer than non-obese adults, while obese adults infected with flu who were only mildly ill or had no symptoms shed influenza A virus for 104% longer than those who were not obese.
Obesity only appeared to affect the duration of viral shedding of the influenza A viruses, one of two types of flu viruses that can cause epidemics in humans.
No association was found for the influenza B virus, which typically causes less serious illness in adults and does not cause pandemics.
Obesity also did not appear to affect the duration of viral shedding among children.
“This is the first real evidence that obesity might impact more than just disease severity,” said senior study author Aubree Gordon. “It might directly impact transmission as well.”
As obesity can alter the body’s immune response and lead to chronic inflammation, in addition to making breathing more difficult and increasing the need for oxygen, the researchers suggest that this may be how the condition affects influenza risk, severity, and transmission potential.