Obesity May Increase Duration of Influenza A Virus Shedding in Adults

Obesity may play an important role in influenza transmission, highlighting the importance of working toward controlling and preventing the obesity epidemic, according to a study published in The Journal of Infectious Diseases.

The global prevalence of obesity has increased significantly over the last few decades, with the pace rapidly accelerating in recent years. By altering immune function and chronic inflammation and creating mechanical difficulties in breathing and increased oxygen requirements, obesity increases the risk for serious complications and death from influenza virus infections, especially in elderly individuals. With an increasing prevalence of obesity, the number of episodes of prolonged influenza virus shedding may increase, leading to increased opportunities to infect naive and high-risk populations. Therefore, it is even more important to develop effective strategies to prevent and control influenza, especially in the overweight and obese population. This could be challenging because of the poor vaccine responses in this population. This study investigated the effect of obesity on the duration of viral shedding within household transmission studies in Managua, Nicaragua, over 3 influenza seasons: late 2015, 2016/2017, and mid/late 2017.

Data were obtained from 2 studies of households around the Health Center Sócrates Flores Vivias in District II of Managua, Nicaragua: the Household Influenza Transmission Study (HITS) and the Household Influenza Cohort Study (HICS). In total, 1783 people in 320 households were included. The HITS contributed 800 participants from the first 2 seasons, and the HICS contributed 983 participants in 2017. Age groups of participants were 0 to 4 years (n=340), 5 to 17 years (n=631), and 18 to 92 years (n=812). The obesity prevalence varied significantly by age, with 2%, 9%, and 42% of participants’ age 0 to 4, 5 to 17, and 18 to 92 years, respectively. Participating members were monitored intensively for 10 to 13 days once an individual with symptomatic influenza was identified in the household. Daily symptom diaries were recorded for all participants, and up to 5 combined nasal/oropharyngeal swab specimens and temperatures were measured for each household contact during follow-up, regardless of symptoms.

Obese individuals with influenza tended to have more symptomatic/severe illness and were less likely to demonstrate asymptomatic influenza, although the differences were not significant. Among nonobese individuals, 16.5% were paucisymptomatic (1 symptom, not including fever) and 18.7% were asymptomatic. Among obese adults, 3.6% were paucisymptomatic and 16.1% were asymptomatic. Among those with ≤1 symptom, not including fever, obese adults shed influenza A virus 104% longer than nonobese adults. Further, symptomatic obese adults shed influenza A virus 42% longer than nonobese adults, with predicted mean shedding period of 5.23 days vs 3.68 days. Symptomatic obese adults also shed influenza A (H1N1) virus 43% longer than nonobese adults. No association was observed between obesity and shedding duration for influenza B virus. Obesity was not associated with shedding duration in children age 5 to 17 years and there were not enough obese secondary children age <5 years to include in the analysis.

Overall, the investigators concluded that, “Obesity may play an important role in influenza transmission, especially as the prevalence of obesity rises, and may be an important target for intervention and prevention strategies.”

Reference

Maier HE, Lopez R, Sanchez N, et al. Obesity increases the duration of influenza A virus shedding in adults [published online August 2, 2018]. J Infect Dis. doi: 10.1093/infdis/jiy370