title: 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 mixed-effect 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; beta, +0.86 [95% confidence interval, +0.03 to +1.68]). Viral RNA concentration demonstrated a nonlinear decrease with time; 26% of oseltamivir-treated 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 beta [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<.05) and viral RNA clearance at 1 week (odds ratio, 0.10 [95% confidence interval, 0.03-0.35] and 0.30 [0.10-0.90] for patients treated on day 1-2 and day 3-4, respectively). Conversely, major comorbidities and systemic corticosteroid use for asthma or chronic obstructive pulmonary disease exacerbations were associated with slower viral clearance. Viral RNA clearance was associated with a shorter hospital stay (7.0 vs 13.5 days; P=.001).
  
  
  CONCLUSIONS
  Patients hospitalized with severe influenza have more active and prolonged viral replication. Weakened host defenses slow viral clearance, whereas antivirals started within the first 4 days of illness enhance viral clearance.
authors: Department of Medicine and Therapeutics, Stanley Ho Centre for Emerging Infectious Diseases, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong.
authors: Nelson
authors: N
authors: Lee
authors: Paul K S
authors: PK
authors: Chan
authors: David S C
authors: DS
authors: Hui
authors: Timothy H
authors: TH
authors: Rainer
authors: Eric
authors: E
authors: Wong
authors: Kin-Wing
authors: KW
authors: Choi
authors: Grace C Y
authors: GC
authors: Lui
authors: Bonnie C K
authors: BC
authors: Wong
authors: Rita Y K
authors: RY
authors: Wong
authors: Wai-Yip
authors: WY
authors: Lam
authors: Ida M T
authors: IM
authors: Chu
authors: Raymond W M
authors: RW
authors: Lai
authors: Clive S
authors: CS
authors: Cockram
authors: Joseph J Y
authors: JJ
authors: Sung
mesh_terms: D000368:Aged; D000375:Aging; D000998:Antiviral Agents / Q000627:therapeutic use; D006760:Hospitalization; D006801:Humans; D053122:Influenza A Virus, H3N2 Subtype; D007251:Influenza, Human / Q000821:virology*; D008297:Male; D008875:Middle Aged; D053139:Oseltamivir / Q000627:therapeutic use; D011446:Prospective Studies; D013997:Time Factors; D019562:Viral Load; D017201:Virus Shedding
chemical_list: D000998:Antiviral Agents; D053139:Oseltamivir