Saverio Caini a , Q Sue Huang b , Meral A Ciblak c , Gabriela Kusznierz d , Rhonda Owen e , Sonam Wangchuk f , Cláudio M P Henriques g , Richard Njouom h , Rodrigo A Fasce i , Hongjie Yu j , Luzhao Feng j , Maria Zambon k , Alexey W Clara l , Herman Kosasih m , Simona Puzelli n , Herve A Kadjo o , Gideon Emukule p , Jean-Michel Heraud q , Li Wei Ang r , Marietjie Venter s , t , Alla Mironenko u , Lynnette Brammer v , Le Thi Quynh Mai w , François Schellevis a , Stanley Plotkin x , John Paget a , on behalf of the Global Influenza B Study
10 August 2015
Literature on influenza focuses on influenza A, despite influenza B having a large public health impact. The Global Influenza B Study aims to collect information on global epidemiology and burden of disease of influenza B since 2000.
Twenty-six countries in the Southern ( n = 5) and Northern ( n = 7) hemispheres and intertropical belt ( n = 14) provided virological and epidemiological data. We calculated the proportion of influenza cases due to type B and Victoria and Yamagata lineages in each country and season; tested the correlation between proportion of influenza B and maximum weekly influenza-like illness (ILI) rate during the same season; determined the frequency of vaccine mismatches; and described the age distribution of cases by virus type.
The database included 935 673 influenza cases (2000–2013). Overall 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 (>20% of total detections), Victoria and Yamagata lineages predominated during 64% and 36% of seasons, respectively, and a vaccine mismatch was observed in ≈25% of seasons. Proportion of influenza B was inversely correlated with maximum ILI rate in the same season in the Northern and (with borderline significance) Southern hemispheres. Patients infected with influenza B were usually younger (5–17 years) than patients infected with influenza A.