Oseltamivir resistance among influenza viruses: surveillance in northern Viet Nam, 2009–2012

Introduction: Antiviral resistance has been reported in seasonal influenza A viruses and avian influenza A(H5N1) viruses in Viet Nam, raising concerns about the efficacy of treatment. Methods: We analysed specimens from two sources during the period 2009–2012: influenza-positive samples from influenza-like illness patients at sentinel clinics in northern Viet Nam and isolates from patients with confirmed A(H5N1) infections. Pyrosequencing was used to detect mutations: H275Y [for A(H1N1) and A(H5N1)], E119V [for A(H3N2)] and I117V [for A(H5N1)]. A neuraminidase inhibition assay was used to determine the Inhibitory Concentration 50 (IC50) values for all influenza A and B isolates. Results: There were 341 influenza A positive samples identified; influenza A(H1N1)pdm09 was identified most frequently (n = 215). In 2009, oseltamivir resistance was observed in 100% (19 of 19) of seasonal A(H1N1) isolates and 1.4% (3/215) of A(H1N1)pdm09 isolates. This H275Y mutation was not found in influenza subtypes A(H5N1) or A(H3N2) isolates. Discussion: In Viet Nam, seasonal and A(H5N1) influenza vaccines are not currently available; thus, effective treatment is required. The presence of oseltamivir-resistant viruses is therefore a concern. Active surveillance for oseltamivir resistance among influenza viruses circulating in Viet Nam should be continued.

Evaluation of Two Lateral-Flow Chromatographic Membrane Immunoassays for Rapid Detection of Influenza Virus in Limited Respiratory Specimens / 임상검사와정도관리

BACKGROUND: The diagnosis of influenza based on clinical grounds alone may be inaccurate, because the presenting symptoms of influenza are similar to those caused by other infectious agents. We evaluate two influenza rapid tests, SD BIOLINE Influenza Ag (Standard Diagnostic inc., Yongin, Korea) and QuickVueTM Influenza Test (Quidel corporation, San Diego, USA) with influenza virus culture and RT-PCR. METHODS: The two commercially available rapid test kits, SD BIOLINE Influenza Ag and QuickVueTM Influenza Test, for influenza virus detection were evaluated with 189 respiratory specimens collected during Dec. 2004 to Nov. 2005 in Vietnam and compared with viral culture and RT-PCR. RESULTS: Overall, the SD BIOLINE Influenza Ag and QuickVueTM Influenza Test showed high sensitivities (88.4% and 82.6%, respectively) and high specificities (99.0% and 99.0%, respectively), high positive predictive value (PPV) (98.7% and 98.6%, respectively) and high negative predictive value (NPV) (91.1% and 87.2%, respectively). CONCLUSION: Both SD BIOLINE Influenza Ag and QuickVueTM Influenza Test were easy to perform and showed high sensitivity and can be used as an additional tool for rapid diagnosis of influenza virus.

Enteroviruses isolated in patients with acute respiratory infections

In 2004, 185 specimens of patients with acute respiratory illnesses that were tested negative to influenza viruses were isolated to determine enteroviruses. The results showed that 10.8% were positive with enteroviruses. These isolated enteroviruses consist of 13 Coxsackievirus B, 1 Echovirus, 1 Poliosabin type 1, and 5 untyped Enteroviruses. The result also showed that 8.1% of isolated viruses were Adenoviruses