Epidemiology of influenza virus reinfection in Guangxi, China: a retrospective analysis of a nine-year influenza surveillance data

Background: Epidemiological characteristic profile of the reinfection of the influenza virus has not been well described. Methods: This study included all influenza cases of Guangxi, China from January 2011–December 2019 that were recorded in the National Notifiable Infectious Disease Reporting Information System (NIDRIS) within 24 hours after diagnosis. Results: A total of 53,605.6 person-months and the median time of 8.7 months were observed for reinfection. The median age at the first influenza virus infection was 4.5 (interquartile range=2.0–7.5) years. The cumulative reinfection incidence was 2% at 6 months, 4% at 12 months, 5% at 24 months, and 7% after 59 months. Living in the rural area (hazard ratio [HR]=1.37 [95% confidence interval (CI), 1.29-1.45]), age ≤6 years (HR=11.43 [95% CI, 9.47–13.80]) were independent risk factors associated with influenza reinfection. Among 49 patients experiencing two laboratory tests, 32 patients (65.3%) were found to be infected with different virus types. The interval between two consecutive laboratory-confirmed episodes of the four groups differed (p=0.148): the maximum was 72.9 months and the minimum was 1.2 months. Conclusions: The reinfection of the influenza virus in Guangxi was independently and positively associated with living the rural area and younger age. The unusually high frequency of reinfection points to a need for further prospective longitudinal studies to better investigate the sufficient impact on different subtypes.