Exploring Neighborhood Level Variation in Incidence and Secondary Transmission of Seasonal Influenza

Influenza epidemics in the United States, are major causes of morbidity and mortality, and cause serious economic disruption on an annual basis. Evidence has begun to accumulate linking neighborhood-level socioeconomic disadvantage to higher rates of hospitalization and mortality related to influenza (Cordoba & Aiello, 2016; Jung, Lin, & Viswanath, 2013). Some studies suggest that this may be due to lower rates of vaccination, higher rates of comorbidities in socioeconomically disadvantaged communities (Cordoba & Aiello, 2016; Jung, Lin, & Viswanath, 2013; Ross & Mirowsky, 2001). However, few studies have evaluated the effects of neighborhood level socioeconomic disadvantage and structural features on influenza incidence in a manner that controls for vaccination status and comorbidities due to a lack of robust surveillance for influenza incidence at the community level. Through secondary analysis of influenza cases collected from the Household Influenza Vaccine Effectiveness (HIVE) study, this study evaluated the impact of census-block level social disadvantage on incidence of primary and secondary influenza infection while controlling for individual and household-level features known to impact individual influenza. Data from the 2010 Census and American Community Survey was used to calculate neighborhood disadvantage z-scores. All respiratory illness meeting case definitions between October 2014- May 2015 were tested for influenza by RT-PCR. Sequential logistic regression models were used to evaluate the effect that neighborhood has beyond individual and household-level risk factors. Individual overall influenza risk and vaccination status varied by age, race, and presence of a high-risk health condition. Results from sequential logistic regression analysis of neighborhood-level variation suggested that while neighborhood level z-score and subjective social position of individual participants was not predictive of primary or secondary influenza incidence, increasing body-mass index (BMI) was statistically significantly protective against primary influenza in adult participants. The relatively small sample size, and limited diversity of socioeconomic status within the initial study sample somewhat limit the generalizability of the results of this study. In light of these limitations, these results suggest a need for further investigation of the link between increasing BMI and influenza incidence, as this could be important in the United States where obesity is rapidly increasing. Further, these results suggest a need for additional study in more diverse populations to definitively determine whether or not neighborhood disadvantage has any impact on influenza incidence