Obesity Could Extend Duration of Influenza A Viral Shedding

As obesity rates continue to climb in all areas of the world, clinicians are becoming more concerned about the serious health risks that are associated with obese adults.

A team of international investigators have found that obese adults shed influenza A virus for 1.5 days longer than nonobese adults, which could potentially increase the likelihood of transmitting the disease. The investigators hypothesize that chronic inflammation caused by obesity is connected with a longer duration of viral shedding.

The research, published in the Journal of Infectious Diseases, drew conclusions from the analysis of data yielded from 2 household influenza studies which were conducted in Managua, Nicaragua. The Nicaraguan studies monitored participating household patients for 10 to 13 days after a symptomatic case of influenza was identified in the household.

A total of 1783 individuals participated from 320 households. Participants ranged in age from 0 to 92 years. Forty-two percent (812) of the participants were defined as adults (aged 18 to 92 years.) Symptoms were recorded for all participants and up to 5 combined nasal/oropharyngeal swab specimens were collected during follow up.

Investigators used parametric accelerated failure time models with Weibull distributions to calculate event time ratios to compare shedding duration in obese vs nonobese adults. The investigators found that symptomatic obese adults shed influenza A 42% longer with a predicted mean shedding of 5.23 days compared with 3.68 days predicted mean shedding of nonobese adults. Additionally, obese adults shed influenza A (H1N1) virus 43% longer than nonobese adults. Furthermore, in participants with mild or no symptoms, obese adults were found to shed influenza A virus 104% longer than nonobese adults.

No association was observed between obese adults and duration of shedding for influenza B virus.

The investigators looked for any patterns in obese children, due to the fact that children 0 to 4 years of age are known to shed influenza 40% longer than adults and children 5 to 17 years of age shed influenza 30% longer than adults. However, the investigators did not find an association between obesity and shedding duration in children between 5 and 17 years of age and there were not enough participants under 5 years of age to draw a conclusion for that age population.

These results reinforce the hypothesis that chronic inflammation in obese patients—which can increase with age—could potentially lead to a longer duration of viral influenza A shedding.

One limitation of the study was that nose and throat samples were only collected from study participants every 2 to 3 days. Furthermore, shedding was measured by reverse transcription polymerase chain reaction analysis which only measured the presence of viral RNA and did not indicate whether the virus was infectious.

“The researchers are continuing to study the correlation between obesity, inflammation and viruses,” a recent news release issued by the National Institute of Allergy and Infectious Diseases reads, “However, they note that reducing obesity rates could be an important target to limit the spread of viral infectious diseases.”

Obesity rates range widely throughout the world, according to study authors. In 2014, rates of adult obesity in the United States was 35.5%, compared with 17.4% in Nicaragua and 4.4% in other low-income countries.