title: Increasing similarity in the dynamics of influenza in two adjacent subtropical Chinese cities following the relaxation of border restrictions.
abstract: The drivers of influenza seasonality remain heavily debated, especially in tropical/subtropical regions where influenza activity can peak in winter, during the rainy season, or remain constant throughout the year. We compared the epidemiological and evolutionary patterns of seasonal influenza epidemics in Hong Kong and Shenzhen, two adjacent cities in subtropical southern China. This comparison represents a unique natural experiment, as connectivity between these two cities has increased over the past decade. We found that, whilst summer influenza epidemics in Shenzhen used to peak 1-3 months later than those in Hong Kong, the difference decreased after 2005 (P<0.0001). Phylogenetic analysis revealed that influenza isolates from Shenzhen have become genetically closer to those circulating in Hong Kong over time (P = 0.045). Furthermore, although Shenzhen isolates used to be more distant from the global putative source of influenza viruses than isolates from Hong Kong (P<0.001), this difference has narrowed (P = 0.02). Overall, our study reveals that influenza activities show remarkably distinct epidemiological and evolutionary patterns in adjacent subtropical cities and suggests that human mobility patterns can play a major role in influenza dynamics in the subtropics.
authors: Stanley Ho Centre for Emerging Infectious Diseases, School of Public Health and Primary Care, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China.|Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, MD 20892, USA.
authors: Yi
authors: Y
authors: Tan
authors: School of Public Health, University of Hong Kong, Hong Kong, China.
authors: Tommy Tsan-Yuk
authors: TT
authors: Lam
authors: Shenzhen Center for Disease Control and Prevention, Shenzhen 518055, Guangdong, China.
authors: Chunli
authors: C
authors: Wu
authors: Stanley Ho Centre for Emerging Infectious Diseases, School of Public Health and Primary Care, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China.
authors: Shui-Shan
authors: SS
authors: Lee
authors: Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, MD 20892, USA.
authors: Cécile
authors: C
authors: Viboud
authors: Shenzhen Center for Disease Control and Prevention, Shenzhen 518055, Guangdong, China.
authors: Renli
authors: R
authors: Zhang
authors: Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT 06520, USA.|Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health, Bethesda, MD 20892, USA.
authors: Daniel M
authors: DM
authors: Weinberger
mesh_terms: D002681:China / Q000453:epidemiology; D002947:Cities; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000302:isolation & purification; D053122:Influenza A Virus, H3N2 Subtype / Q000235:genetics / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology; D012621:Seasons; D014195:Travel