Int J Infect Dis . Global variation in early epidemic growth rates and reproduction number of seasonal influenza

[tetano]

Int J Infect Dis


. 2022 Jun 16;S1201-9712(22)00354-X.
doi: 10.1016/j.ijid.2022.06.022. Online ahead of print.
Global variation in early epidemic growth rates and reproduction number of seasonal influenza


R Thompson ¹ , J G Wood ¹ , S Tempia ² , D J Muscatello ³



Affiliations

• PMID: 35718299
• DOI: 10.1016/j.ijid.2022.06.022

Abstract

Introduction: Little is known about global variation in early epidemic growth rates and effective reproduction numbers (R_e) of seasonal influenza. We aimed to estimate global variation in R_e of influenza type A and B during a single period.
Methods: Country influenza detection time series from September 2017 through January 2019 were obtained from an international database. Type A and B epidemics by country were selected based on R_e estimates for a five-week moving window advanced by week. Associations of R_e with absolute latitude, Human Development Index, percent of the population aged <15 years and percent living rurally in each country were assessed.
Results: Time series were included for 119 of 169 available countries. There were 100 countries with influenza A and 79 with B epidemics. Median R_e for both influenza A and B epidemics was 1.23 (ranges: A 1.10, 1.60; B 1.06, 1.58). R_e of influenza B, but not A, was independently associated with absolute latitude, increasing by 0.022 (95% CI 0.002, 0.043) per 10 degrees.
Conclusions: R_e of influenza A and B were similar. Only R_e of influenza B was associated with country characteristics; increasing with distance from the equator. The approach may be suitable for continuous R_e surveillance.

Keywords: Effective reproduction number; Epidemic dynamics; Geographic variation; Influenza type; Seasonal influenza.