A very recent and very powerful study was recently published in the open-access journal: PLOS Pathogens, one of the top journals on Microbiology and Infectious disesases…
Stochastic Processes Are Key Determinants of Short-Term Evolution in Influenza A Virus
The article is not very easy and is full of terms that need background knowledge, but you should get a good idea on the work from the Abstract (Synopsis) and Introduction.