Clinical characteristics and outcomes during a severe influenza season in China during 2017–2018

BACKGROUND: A severe seasonal influenza epidemic was observed during 2017–2018 in China, prompting questions on clinical characteristics and outcomes of severe cases with influenza. METHODS: We retrospectively collected clinical data and outcomes of laboratory-confirmed hospitalized patients (severe to critical) during Jan-2011 to Feb-2018 from five hospitals, followed by a systematic analysis of cases from 2017 to 2018 (n = 289) and all previous epidemics during 2011–2017 (n = 169). RESULTS: In-hospital fatality was over 5-folds higher during the 2017–2018 (p < 0.01) in which 19 patients died (6.6%), whereas only 2 mortalities (1.2%) were observed during 2011–2017. Of the 289 hospitalized in 2017–2018, 153 were confirmed with influenza B virus, 110 with A/H1N1pdm09, and 26 A/H3N2, whereas A/H1N1pdm09 was the predominant cause of hospitalization in previous seasons combined (45%). Fatal cases in 2017–2018 were exclusively associated with either influenza B or A/H1N1pdm09. Our results show that a significant lower proportion of patients aged 14 or greater were treated with oseltamivir, during the 2017–2018 epidemic, and exhibited higher levels of clinical severity. CONCLUSIONS: In-hospital fatality rate might be significantly higher in the 2017–2018 season in China. A sufficient supply of oseltamivir and antiviral therapy within 48 h from onset could reduce fatality rates. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12879-019-4181-2) contains supplementary material, which is available to authorized users.