Before revision:  Of 24 articles qualifying for inclusion, four main  objectives were identified: estimating transmission parameters ( 9 studies), assessing determinants of transmission ( 4 ), examining consequences of hypothetical outbreaks ( 3 ), and assessing alternative control strategies ( 8). Population-based ( 11) , metapopulation (5), and individual-based (8) model frameworks were represented. The majority of models (18) were parameterized to the genotype II isolates currently circulating in Europe and Asia.
After revision:  Of 24 articles qualifying for inclusion, four main objectives were identified: estimating transmission parameters ( 9 studies), assessing determinants of transmission ( 4 ), examining consequences of hypothetical outbreaks ( 3 ), and assessing alternative control strategies ( 8). Population-based ( 11) .