Influenza B Lineages Circulating among Children Attending Yangon Children’s Hospital

Influenza B viruses have also caused a considerable number of paediatric deaths although they are generally less prevalent than influenza A viruses. This cross-sectional study aimed to determine trends in prevalence of influenza B lineages among children attending Out Patient Department of Yangon Children’s Hospital. Nasopharyngeal swabs were collected from 316 children with influenza-like illness (ILI) during January 2016 to October 2018. Influenza A and influenza B viruses were detected by conventional reverse transcription-polymerase chain reaction (RT-PCR) targeting matrix gene. Lineages of influenza B virus were identified by conventional RT-PCR targeting haemagglutinin gene. Influenza B virus accounted for 6.5% (10/153), 1.5% (1/68) and 2.1% (2/95) of all ILI cases and 45.5% (10/22), 8.3% (1/12) and 25% (2/8) of influenza virus positive ILI cases in 2016, 2017 and 2018 (up to October), respectively. Age and sex preponderance were not seen among influenza B virus-infected children. Fever, cough and rhinorrhoea were found as main but non-specific symptoms. Majority of influenza B virus-infected children were seen in June, July and August suggesting timing for influenza vaccination. All ten cases of influenza B virus detected in 2016 and the only case in 2017 were of B/Victoria lineage whereas both cases in 2018 were of B/Yamagata lineage highlighting the changing epidemiology of influenza B/lineages in the recent years. This study generated information useful for assessment of influenza B outbreaks, timing for influenza vaccination and selection of influenza vaccine for use in subsequent years in Myanmar.