Validation of a Definition for K-12 Student Absenteeism Due to Influenza-like Illness (ILI) for School-based Influenza Activity Monitoring in Oregon School District, Wisconsin—ORCHARDS (Oregon Child Absenteeism and Respiratory Disease Study)

Syndrome-based absenteeism monitoring is proposed as an approach for early identification of influenza outbreaks in schools and surrounding communities, utilizing routinely collected attendance data. The availability of a simple, valid definition of ILI-related absence (a-ILI) is a prerequisite for monitoring. We conducted a prospective study in children aged 4–19 years, between January 5, 2015 and April 11, 2017, which enrolled students with acute respiratory illness (ARI). Via home visits, the study team assessed participating students for symptoms (fever, cough, sore throat, nasal congestion, runny nose), collected nasal swabs for multiplex PCR testing, and ascertained school absence status. For analysis, ILI was defined as the presence of fever and a respiratory tract symptom (cough, sore throat, nasal congestion, or runny nose). We used multivariate binary logistic regression to assess the relationships between pathogens, absence status, and illness category. Of the total 661 participating students, 622 with ARI onset during school semesters remained in the analysis. Having an ILI was associated with absenteeism (Χ2=87.70; P < 0.001), and with PCR detection of influenza A (FluA) and B (FluB), adenovirus (AD), and rhinovirus/enterovirus (R/E) (Table). While FluA, FluB, and AD were associated with positive likelihoods of a-ILI, the presence of R/E was associated with a negative likelihood of a-ILI. PCR detection of either FluA or Flu B was strongly associated with a-ILI (OR=4.84; 95% CI: 2.80–8.34; P < 0.001). A simple definition for a-ILI (absent with fever and a respiratory symptom) is strongly associated with laboratory-confirmed influenza. Accordingly, a-ILI may serve as a proxy for influenza-specific absenteeism, thus allowing school-based absenteeism monitoring for influenza outbreaks. All authors: No reported disclosures.