We've posted a new paper to the arXiv on analyzing trait evolution across a phylogeny using Felsenstein's latent liability model. This model allows discrete traits and continuous traits to be incorporated into the same framework and correlations assessed. I played only a small role in compiling data and helping with the analysis of epitope evolution in influenza. Here, we find abundant coevolution at amino acid sites responsible for the virus's immunological phenotype. This suggests mutating away from human immunity may depend on controlling epistatic interactions among sites, likely making antigenic escape more difficult for the virus.