Investigation of the First Two Cases of Oseltamivir- Resistant Pandemic (H1N1) 2009 Virus in Taiwan

Hui-Chen Lin

2009 Vol.25 NO.12

Correspondence Author: Jih-Haw Chou


The outbreak of pandemic (H1N1) 2009 occurring in the Mexico-United States border in April 2009 resulted in worldwide spreading within six weeks. As of November 15, 2009, there are over 6,770 confirmed deaths in the world. Fortunately, the current circulating strains of the virus are shown to be sensitive to the influenza virus neuraminidase inhibitors oseltamivir and zanamivir. However, since July 2009, the World Health Organization (WHO) has started to receive reports of oseltamivir-resistant pandemic (H1N1) 2009 viruses. All of the cases have a mutation in the neuraminidase gene resulting in an amino acid change from histidine to tyrosine at amino acid 275 (referred to as H275Y). The viruses have been shown to be resistant to oseltamivir, but they remain sensitive to zanamivir. After analyzing the 32 oseltamivir- resistant cases, the WHO determined that these cases are sporadic and not circulating at a community level. As of November 12, there are five cases of oseltamivir-resistant pandemic (H1N1) 2009 viruses detected in Taiwan. All of the isolates were taken from the severe complicated cases, which have finally reached full recovery. Extensive investigation of the five cases suggests that such viruses are sporadic and not spreading in the community. This study is aimed to report the findings of the investigation of the first two cases of oseltamivir-resistant pandemic (H1N1) 2009 in Taiwan; another main objective is to remind clinicians to be aware of oseltamivir-resistant pandemic (H1N1) 2009 viruses, especially when patients have had >5 days of antiviral treatment and still have unresolved or complicated illnesses. Keywords: resistance; pandemic (H1N1) 2009 virus; antiviral medications