The natural viral load profile of patients with pandemic 2009 influenza A(H1N1) and the effect of oseltamivir treatment

Abstract

Background; The natural history of viral shedding from the upper respiratory tract of the new pandemic 2009 influenza A(H1N1) and the effect of oseltamivir treatment were uncertain. Methods: A retrospective cohort study involving 145 consecutive palienls with specimens positive by reverse transcriptase-polymerase chain reaction for the matrix and new III genes was conducted. Results: The nonlrealed and osellamivir-trcalcd palienls were comparable in their viral load al presentation, demography, and the presenting symptoms. No correlation was observed between viral load with age and number of symptoms. Viral load of nasopharyngeal aspirate (NPA) was significantly lower in treated than in nonlrealed palienls al day 5 after symptom onset. When oseltamivir was initiated ≤2 days after symptom onset, a greater rate of viral load reduction in NPA of treated patients than that of nontreated patients was observed (-0.838 [95% Cl, -0.809 to -0.466] vs -0.409 [95% CI, -0.863 to -0.1851 log 10 copies/mL/d post-symptom onset), and the viral load was undetectable at day 8 after oseltamivir initiation, which was I day earlier than that of those whose treatment was initiated > 2 days of symptom onset. The viral load was inversely correlated with concomitant absolute lymphocyte count in nontreated patients (Pearson correlation coefficient [r] = -0.687, P = .001) and lrealed palienls (Pearson r = -0.365, P< .001). Resolution of fever was 1.4 days later in nontreated lhan treated palienls (F=.012) Conclusions: The natural viral load profile was described. Oral oseltamivir suppresses viral load more effectively when given early in mild cases of pandemic 2009 influenza A(HlNl) infections. © 2010 American College of Chest Physicians.