Influenza associated mortality in Southern China, 2010-2012.

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.