Shedding of the Pandemic Swine-Origin Influenza A Virus (H1N1) after Oseltamivir Administration

We analyzed the virus shedding of an oseltamivir-treated patient who had been infected with the pandemic swine-origin influenza A (H1N1) virus which had an oseltamivir-sensitive neuraminidase. The virus was isolated from the pharyngeal swabs of the patient using MDCK cells, and the virus genome RNA was detected in the same samples both by real-time RT-PCR and RT-PCR. The virus was isolated until 44 h after oseltamivir administration although the virus genome was detected until one day after oseltamivir treatment was stopped. Due to their high sensitivity, RT-PCR and real-time RT-PCR may cause misdiagnosis by detection of viral genome which does not infect, and classical virus isolation and clinical symptoms are recommended for the evaluation of oseltamivir treatment. 1. Introduction The novel swine origin influenza A virus (S-OIV) (H1N1) caused pandemic in 2009-2010 [1]. Oseltamivir (Tamiflu, Hoffmann LaRoche) is recommended for the treatment of S-OIV infection because it is naturally resistant to amantadine and rimantadine but is susceptible to the neuraminidase inhibitors, oseltamivir, and zanamivir (Relenza, Glaxo Smithkline) although the oseltamivir-resistant neuraminidase (NA) H275Y (N1 numbering) was detected in some isolates [2–4]. Here, we precisely report the virus shedding of the pandemic S-OIV after oseltamivir treatment (Table 1). Table 1: Symptoms and detection of S-OIV. 2. Case Presentation A 24-year-old female in Shanghai, China was infected with the pandemic S-OIV in September 2009. She had received a seasonal flu vaccination (Sanofi Pasteur) the previous year. Her first symptom was a sore throat, and on the 4th day after the onset of her sore throat, she had a high fever (>38.5°C). The next day (the 5th day after onset), she visited a clinic. Her blood cell count was normal. Her chest X-ray did not show bronchitis or pneumonia. Oseltamivir (75？mg × 2) was administered at 36 hours after the onset of her high fever for five days. On the second day of oseltamivir administration, her high fever disappeared, and all eight segments of the S-OIV genome were cloned from her pharyngeal swabs, and the sequences of the pandemic S-OIV were confirmed. Its neuraminidase (NA) contained an oseltamivir-sensitive sequence (275H). Since then, pharyngeal swabs were collected everyday for eight days and subjected to virus isolation and examined for virus genome RNA (from the 6th to the 13th day). Each pharyngeal swab was aliquoted into three fractions: for virus isolation, for RT-PCR, and for real-time RT-PCR, and each experiment was performed in a