Heat map of hierarchical clustering analysis of differentially expressed genes in infected NPTr cells. Genes differentially expressed were subjected to hierarchical clustering (complete linkage method) using uncentered correlation as similarity measure. (A) Horizontal rows represent individual genes and vertical columns represent individual samples from mock-infected, S. suis, H1N1, S. suis/H1N1 (n = 4). (B) Interesting genes are zoomed in from the heat map in A. Color scale: black, average signal intensity; brightest blue and brightest yellow indicate low and high expression levels, respectively.