Quantification of viral load in clinical specimens collected from different body sites of patients infected with influenza viruses

Abstract

Viral shedding profile of infections caused by the novel influenza A (pH1N1) virus has not been extensively studied. In the present study we aimed to compare the influenza viral load in clinical specimens collected from different body sites of patients to analyze the best specimen for detecting viral load and predicting disease severity. The respiratory specimens (throat and nasal swabs), urine and serum were collected from patients on first day of their hospital visit within 48 h of onset of influenza like illness (ILI) and screened for influenza positivity in respiratory specimens by real-time RTPCR. A total of 10 pandemic H1N1 and 15 seasonal influenza positive cases were included in this study and viral load was estimated in all the types of specimens by real-time RT-PCR. Our findings revealed that the nasal swab had the highest mean viral load of 21.406 × 10⁴ followed by throat swab (12.777 × 10⁴), urine (0.026 × 10⁴), serum (0.0007 × 10⁴). These findings confirm that nasal secretions are the best specimen, followed by throat swab, urine and serum. The importance of this study is to show the viral shedding profile in different specimen types and to suggest alternatives to respiratory specimens for the diagnosis of influenza.