Main features of influenza surveillance systems of countries and sub-national regions included in the analysis.

<p>The Global Influenza B Study, Latin-American countries, 2003–2014.</p

Heat map of monthly influenza virus incidence patterns, 2003–2014, sorted by latitude.

<p>The Global Influenza B Study, Latin-American countries, 2003–2014.</p

Timing and amplitude of primary and secondary peaks of seasonal influenza epidemics.

<p>The Global Influenza B Study, Latin-American countries, 2003–2014.</p

Countries and sub-national regions that were included in the analysis.

<p><b>The Global Influenza B Study, Latin-American countries, 2003–2014</b>. Dark Blue: Central America. Light Blue: Brazil. Yellow: remaining sites in South America.</p

Timing and amplitude of primary (circles) and secondary (triangles) peak of influenza detection by site, against their latitudinal position.

<p><b>The size corresponds to the amplitude of influenza seasonality</b>. Dark Blue: Central America. Light Blue: Brazil. Yellow: remaining sites in South America.</p