In general terms, a change in your genome sequence can mean a small alteration, like removing or adding a single link in a chain, or it can mean a structural change involving bigger chunks, like removing or adding whole sections of the chain.
This would change when the virus crossed paths with cells containing a very specific DNA sequence, a sequence that would act as a molecular key to unlock secondary functions that were not so benign.
Because automated actions must be reprogrammed with new coding each time the sequence of steps changes, it often does not make sense for IT departments to automate tasks that frequently change or are reactive.