Clinical symptoms, comorbidities and health outcomes among outpatients infected with the common cold coronaviruses versus influenza virus

Background: Common cold coronaviruses (ccCoVs) and influenza virus are common infectious agents causing upper respiratory tract infections (RTIs). However, clinical symptoms, comorbidities, and health effects of ccCoV infection remain understudied. Methods: A retrospective study evaluated 3,935 outpatients with acute upper RTI at a tertiary teaching hospital. The presence of ccCoV and influenza virus was determined by multiplex molecular assay. The demographic, clinical symptoms, and health outcomes were compared between patients with ccCoV (n = 205) and influenza (n = 417) infections. Multivariable logistic regression was employed to evaluate predictors and health outcomes over a one-year follow-up. Results: Sore throat, nasal discharge, headache, and myalgia were more predominant in ccCoV infection; fever was common in influenza. Most patients reported moderate symptoms severity (49.8% ccCoV, 56.1% influenza). Subsequent primary care visits with symptoms of RTI within a year were comparable for both infections (27.3% ccCoV vs. 27.6% influenza). However, patients with influenza reported increased primary care visits for non-RTI episodes and all-cause hospital admission. Baseline comorbidities were associated with increased primary care visits with symptoms of RTI in either ccCoV (adjusted odds ratio [aOR] 2.5; 95% confidence interval [CI] 1.1–5.9; P = 0.034) or influenza (OR 1.9; 95% CI 1.1–3.1; P = 0.017) infections, due probably to the dysregulation of the host immune response following acute infections. In patients infected with influenza infection, dyslipidemia was a predictor for subsequent primary care visits with symptoms of RTI (unadjusted OR 1.8; 95% CI 1.0–3.0; P = 0.040). Conclusions: Both influenza and ccCoV infection pose significant disease burden, especially in patients with comorbidities. The management of comorbidities should be prioritized to mitigate poor health outcomes in infected individuals.