Hoang, P.M.V. et al. 2019. Missed detections of influenza A(H1)pdm09 by real-time RT–PCR assay due to haemagglutinin sequence mutation, December 2017 to March 2018, northern Viet Nam. Western Pacific Surveillance and Response. 10, 1 (Apr. 2019). DOI:https://doi.org/10.5365/wpsar.2018.9.3.003.