Airborne Influenza A Virus Exposure in an Elementary School

Abstract

Influenza contributes significantly to childhood morbidity and mortality. Given the magnitude of the school-aged child population, a sizeable proportion of influenza virus transmission events are expected to occur within school settings. However, influenza virus activity in schools is not wellunderstood, likely due to our limited ability to accurately monitor for respiratory viruses without disrupting the school environment. In this study, we evaluated the use of a bioaerosol sampling method to noninvasively detect and quantify airborne influenza A virus (IAV) densities in a public elementary school. Air samples were collected from multiple locations in the school, two days per week, throughout an eight-week sampling period during influenza season. Real-time RT-PCR targeting the IAV M gene revealed detectable IAV on five occasions in densities ranging from 2.0 × 10 −1 to 1.9 × 10 4 . No significant differences in IAV densities were related to student presence/absence. The majority of IAVassociated particles were ≤4 μm in diameter, and theoretical calculations indicate infectious thresholds after minutes of exposure. Our study represents the first identification and quantification of airborne influenza virus in an elementary school, and the results suggest that airborne IAV has the potential to circulate in schools during influenza season, in large enough doses known to cause infection.Monitoring pathogen exposures in the environment is a longstanding practice to predict and investigate the incidence and spread of infectious diseases. Schools, in particular, have been identified as sources of influenza outbreaks 1-4 , and monitoring influenza-like illness in the school-aged population is a current strategy for predicting communal influenza 5 . In both seasonal and pandemic influenza outbreaks, schoolchildren are often the first to become ill 1,4,6 . Furthermore, modeling studies suggest that the highest incidence of respiratory infection is among school-aged children and young adults who contribute significantly to the spread of infections during the early stages of emerging respiratory epidemics 7 . In some communities, school-centric data, such as the number of student absences (total and those due to illness) and school nurse visits, are recorded and used for early detection of influenza outbreaks 5 . However, due to the inconsistency of self-reported data, the use of student health reports to predict influenza outbreaks is not a standardized practice. Therefore, the development of an effective method to monitor influenza virus in schools is necessary to enhance efforts to manage student and community health.Human behaviors and their environments influence respiratory virus disease susceptibility, severity, and transmissibility 8 , especially among children. Specifically, the high incidence of influenza in children is thought to be related to interactions with schoolmates and siblings 6 , as pathogen transmission is directly related to host proximity and density 9 . Influenza virus is transmitted through (i) di...

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