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Table 3 Between-estimates heterogeneity (as measured by the I2 statistics) for summary relative illness ratio calculated for each influenza virus within each age group, and variables significantly (p<0.05) correlating with them. The Global Influenza B Study, 1999-2014

From: Distribution of influenza virus types by age using case-based global surveillance data from twenty-nine countries, 1999-2014

Influenza virus I2 Variables significantly (p<0.05) correlating with sRIRs
Latitude % of cases accounted for in the same season % of cases accounted for in the previous season Ageing index GDP per capita % of outpatients (a)
Young children (0-4 years)
 A(H1N1) 97.5%       
 A(H1N1)pdm2009 97.8%    
 A(H3N2) 98.2%    
 B 97.5%    
Older children (5-17 years)
 A(H1N1) 95.2%       
 A(H1N1)pdm2009 99.5%    
 A(H3N2) 97.2%     
 B 98.4%  
Young adults (18-39 years)
 A(H1N1) 97.1%      
 A(H1N1)pdm2009 97.5%     
 A(H3N2) 96.0%     
 B 98.1%    
Older adults (40-64 years)
 A(H1N1) 95.2%       
 A(H1N1)pdm2009 98.7%      
 A(H3N2) 93.5%      
 B 96.6%    
Elderly (65+ years)
 A(H1N1) 73.9%       
 A(H1N1)pdm2009 94.7%   
 A(H3N2) 95.2%     
 B 92.4%     
  1. GDP: gross domestic product.
  2. (a)Proportion of outpatients among reported influenza cases