Factors Associated With Influenza in an Emergency Department Setting

Emergency departments (EDs) become more overcrowded during peak respiratory virus season. Distinguishing influenza from other viruses is crucial to implement social distancing practices, early treatment, and prompt disposition.

We sought to determine factors associated with influenza among a prospective cohort of consecutive ED patients with acute respiratory illness (ARI).

Between December 2016 and March 2017, trained research assistants screened consecutive ED patients with ARI symptoms. ARI criteria included measured fever at home or in the ED >38°C and a cough, sore throat, or rhinorrhea with a duration of symptoms >12 hours and <1 week. After consent, research assistants collected demographics and clinical history using a standardized data form, and patients had a polymerase chain reaction-based assay that is nearly 100% sensitive for influenza. Univariate analysis was conducted on all predictor variables. Significant variables were entered into a multivariate logistic regression model to find factors that were independently associated with influenza.

One hundred nineteen patients consented to enrollment and 31% were found to be positive for influenza. Myalgia, the absence of gastrointestinal symptoms (no diarrhea or vomiting), sore throat, chills, headache, and oxygen saturation ≥97% were significant on univariate analysis and were entered into the multivariate model. Myalgia (adjusted odds ratio [AOR] 3.9), the absence of gastrointestinal symptoms (AOR 4.7), and oxygen saturation ≥97% (AOR 2.8) were significant independent factors of influenza.

The presence of myalgia, the absence of gastrointestinal symptoms, and oxygen saturation ≥97% are factors that can help distinguish influenza from other acute respiratory illnesses in the ambulatory ED population.