Analysis of reported confirmed notifiable influenza cases and deaths in China, 2014-2018

Abstract

Objective To analyze the characteristics of reported confirmed notifiable influenza cases and deaths from 2014 to 2018, so as to provide scientific evidences for surveillance and diagnosis of influenza cases. Methods Descriptive analysis was performed for the data of influenza cases with the onset dates within the period between January 1, 2014 and December 31, 2018 collected from the National Notifiable Infectious Diseases Reporting System. Results A total of 1 939 842 influenza cases were reported nationwide from 2014 to 2018, including 631 434 confirmed cases and 1 299 798 clinically diagnosed cases, of which 301 cases died (253 confirmed cases and 48 clinically diagnosed cases). The highest number of confirmed influenza cases was reported among children aged 0-4 years old (225 184 cases) and the lowest was among the elderly aged ≥65 years old (34 071 cases), accounted for 35.66% and 5.40%, respectively. The confirmed deaths mainly distributed among those aged 18-49 years old with 90 cases (35.02%) and the elderly ≥65 years old with 72 cases (28.02%). Nineteen cases (7.39 %) of confirmed deaths were reported among patients of 5-17 years old and was the lowest. The median of interval between onset and diagnosis (MIOD) of confirmed deaths is 6 (3, 10) days, which was longer than the 3 (1, 7) days of confirmed survival cases. The MIOD in the Western Region was 6 (2, 11) days, which was longer than 2 (1, 6) days in the East Region and 3 (1, 7) days in the Middle Region. From 2014 to 2018, the MIOD was shortened from 4 (1, 8) to 2 (1, 5) days. Most influenza virus infected children aged ≤17 years old and more influenza B than influenza A were detected in children. For the confirmed death cases, 79.20% (103/130) were infected by influenza A (H1N1) virus. Conclusions According to the general population of China, the data of influenza incidence and deaths released by the WHO, the notifiable influenza morbidity and deaths were far lower than the well-recognized level in China. For the high risk group of serious influenza complications, once having influenza-like symptoms, laboratory testing should be performed for effective treatment to reduce the risk of serious outcomes. Key words: Influenza; Influenza A virus; Influenza B virus; Notifiable cases