To systematically dissect infection-stage dependent signalling networks, here we performed signature-tagged mutagenesis (STM)-based brain infectivity assay with transcription factor (TF) and kinase mutant libraries using intravenous infection route, which can bypass lung infection, and compared these data with that of previously acquired lung-STM data using the same set of mutant libraries but intranasally infected15,16. Here, TF is linked to infection.