The global influenza B study (GIBS): Sharing data from national surveillance to understand the impact of influenza B disease

Introduction According to World Health Organization (WHO) estimates, annual epidemics result in 3 to 5 million cases of severe illness, and 290,000 to 650,000 deaths worldwide. Traditionally, attention has been directed toward influenza A, which accounts for the majority of influenza cases in most seasons. However, influenza B can represent a considerable proportion of total cases and little is known on the epidemiology of influenza in the tropics. The Global Influenza B Study (GIBS) was launched in 2012 and aimed to collect and analyze information on the epidemiology and burden of disease of influenza B in the world during the past decades and assess differences, in order to support future prevention policies. Methods National surveillance systems in over fifty countries in the Northern, Southern hemispheres and the inter-tropical belt were contacted to join the GIBS study from June 2013 to February 2016. All countries were asked to make data available from their influenza surveillance system during recent years. Each participating country was asked to provide the weekly number of influenza cases reported, broken down by age group and virus type and subtype, and the weekly influenza-like illness (ILI) or acute respiratory infection (ARI) rates per 100,000 population or 100 consultations when available. For large countries, especially when stretched across different climate zones, stratified data by region/province were requested. The proportion of influenza cases due to type B and Victoria and Yamagata lineages in each country and season were calculated; the correlation between the proportion of influenza B cases and maximum weekly ILI rate during the same season was tested; the frequency of vaccine mismatches was determined; and the age distribution of cases by virus type was described. Results Twenty-six countries in the Southern, Northern hemispheres and intertropical belt provided virological and epidemiological data from national surveillance from 2000. The database includes almost 1 million influenza cases. Overall, the median proportion of influenza B was 22.6%, with no statistically significant differences across seasons. During seasons where influenza B was dominant or co-circulated, Victoria and Yamagata lineages predominated during 64% and 36% of seasons, respectively. A vaccine mismatch was observed in a quarter of seasons. Patients infected with influenza B were usually younger than patients infected with influenza A. Regional Latin America analyses showed improvements of characterization of influenza B specimens are needed. There is substantial heterogeneity of spatio-temporal patterns of influenza epidemics. An analysis of the age distribution indicated that influenza B is more frequently detected in school children (5–18), influenza A(H1N1) in small children (0–4), influenza A(H1N1)p in adults and influenza A(H3N2) in the elderly (65 years and older). Conclusion Influenza B is a common disease with some epidemiological differences compared to influenza A. Sharing national surveillance data at a regional or global level is key to understanding the evolution of epidemics and differences of timing between countries. Results from this study should be considered when optimizing control and vaccination strategies in different regions and reducing the global burden of disease due to influenza. Funding statement The study received a funding support from Sanofi Pasteur.