Figure 3: Maximum clade credibility (MCC) trees of the NA lineages in swine.

Timescaled Bayesian MCC trees inferred for the NA segment for the three major swine virus lineages: (a) avian-origin Eurasian N1 swIAV lineage, the (b) classical N1 swIAV lineage and the (c) multiple human seasonal virus-origin N2 swIAV lineages circulating in swine. Branches of human seasonal H3N2 influenza virus origin are shaded grey in c, while branches associated with viruses from swine are shaded by country of origin: Argentina=brown; Canada=red; China (including Hong Kong SAR and Taiwan)=yellow; Europe=black; Japan=pink; Mexico=light blue; South Korea=green; Thailand=orange; USA=dark blue; Vietnam=purple. Posterior probabilities >0.8 are included for key nodes, and international migration events that are supported by high posterior probabilities and long branch lengths are labelled according to Fig. 2.