Pandemic Influenza A (H1N1) 2009 in India: Duration of virus shedding in patients under antiviral treatment.

ABSTRACT

Background: National Centre for Disease Control (NCDC), Delhi, is a national nodal centre for surveillance of pandemic Influenza A (H1N1) in India. The present study was undertaken to see the period of infectivity in positive cases undergoing antiviral therapy. Objective: To assess the duration of virus shedding by real-time polymerase chain reaction (real-time PCR) in some of the positive patients taking Oseltamivir treatment. Materials and Methods: Clinical samples (throat swabs, nasal swabs and nasopharyngeal swabs) collected by the clinicians from patients quarantined in government hospitals in different parts of India are being sent to the designated reference laboratory at Delhi for screening presence of pandemic Influenza virus. The samples are tested by Real-Time PCR using CDC recommended reagents and protocol for confirmation of the H1N1 novel influenza virus. In 150 of the positive cases, we requested the clinicians to send samples for 5 consecutive days after administration of antiviral therapy, to see the trend of therapy response on viral shedding. Samples for more than 5 days were received from patients till they showed no amplification for any of the three target genes (Influenza A, Swine Influenza A or Swine H1). Results and Conclusion: In 99.33% (149/150) cases, the influenza infection resolved within 10 days. Sixty-four percent (96/150) of the positive patients turned negative within 5 days of the start of antiviral treatment. Only one patient belonging to high risk group showed prolonged virus shedding (19 days).