Influenza associated mortality in Southern China, 2010-2012.

Abstract Objective Influenza caused substantial morbidity and mortality worldwide. The mortality burden caused by influenza has been under evaluation; however, data assessing this burden have been relatively sparse in tropical or subtropical regions. We estimated influenza-associated mortality in Guangzhou, China and assessed the excess mortality due to different influenza virus subtypes. Methods We estimated influenza-associated excess mortality due to all-cause, pneumonia and influenza, cardiorespiratory disease and other influenza-associated diagnoses from weekly numbers of deaths and influenza surveillance data through negative binomial regression model during 2010–2012. Results Estimates derived from the model indicated that influenza resulted in 14.72 (95% confidence interval (CI), 12.12–17.31) deaths per 100,000 population per year from all-cause death among all ages group. Most deaths (84.2%) occurred among people aged ≥65 years. B virus caused 5.84 (95%CI, 4.10–7.58) deaths per 100,000 population for all-cause death, which was higher than A (H3N2) (4.89, 95%CI, 3.19–6.59) or A(H1N1)pdm09 (3.99, 95%CI, 2.32–5.66). Conclusions Influenza is responsible for a substantial mortality especially among people aged ≥65 years and influenza B virus caused the highest influenza-associated mortality. The results highlight the need for seasonal influenza vaccination programs in subtropical areas to decrease excess mortality.