Few studies have explored the different lineages of influenza B viruses which cause excess death. This study was aimed to estimate age- and sex-specific excess mortality associated with influenza subtypes/lineages in Shanghai, during 2010-2015.
We used quasi-Poisson regression models to fit weekly numbers of deaths from various causes by adjusting long-term trend, seasonal trend, and absolute humidity as confounding factors. The mortality burden associated with influenza subtypes/lineages was estimated by age and sex.
The average influenza-associated excess mortality rate in deaths coded as all-cause was 27.66(95%CI: 22.30-33.88) per 100,000 person-years. The excess deaths of 6 underlying causes in people aged ≥65 years weight heavily. Compared to influenza B(Victoria) lineage, influenza B(Yamagata) lineage had more effect on influenza-associated disease burden, particularly in patients with respiratory and circulatory diseases. There was no statistical significance in sex in mortality burden associated with influenza.
Excess mortality associated with influenza B virus is dominated by B(Yamagata) lineage in Shanghai and the evidence on sex differences in influenza-associated mortality burden for respiratory and circulatory diseases is limited. Improving vaccinating the elderly and strengthening the laboratory-based surveillance of influenza B lineages in Shanghai are needed to reduce the disease burden of influenza.

Copyright © 2020. Published by Elsevier Ltd.