Viral loads and duration of viral shedding in adult patients hospitalized with influenza

Abstract

Background. The goal of this study was to characterize viral loads and factors affecting viral clearance in persons with severe influenza. Methods. This was a 1-year prospective, observational study involving consecutive adults hospitalized with influenza. Nasal and throat swabs were collected at presentation, then daily until 1 week after symptom onset. Real-time reverse-transcriptase polymerase chain reaction to determine viral RNA concentration and virus isolation were performed. Viral RNA concentration was analyzed using multiple linear or logistic regressions or mixedeffect models. Results. One hundred forty-seven inpatients with influenza A (H3N2) infection were studied (mean age ± standard deviation, 72 ± 16 years). Viral RNA concentration at presentation positively correlated with symptom scores and was significantly higher than that among time-matched outpatients (control subjects). Patients with major comorbidities had high viral RNA concentration even when presenting >2 days after symptom onset (mean ± standard deviation, 5.06 ± 1.85 vs 3.62 ± 2.13 log10 copies/mL; P = .005; β, +0.86 [95% confidence interval, +0.03 to +1.68]). Viral RNA concentration demonstrated a nonlinear decrease with time; 26% of oseltamivirtreated and 57% of untreated patients had RNA detected at 1 week after symptom onset. Oseltamivir started on or before symptom day 4 was independently associated with an accelerated decrease in viral RNA concentration (mean β [standard error], -1.19 [0.43] and -0.68 [0.33] log10 copies/mL for patients treated on day 1 and days 2-3, respectively; P