Hi Lisa,
Here is a link to a
fairly simple explanation of the process for DAAs. The same basics apply to the various different DAAs being used for HCV treatment although the exact mechanism varies a little depending on which one.
esofosbuvir.com/sofosbuvir-drug/sofosbuvir-mechanism-action/
You can also think of it as a bit like a lock and key. Lots of keys will fit the lock but only one will open it and allow the virus to replicate. Normally the virus finds the correct keys in our bodies but if we flood our bodies with lots of faulty keys (Sofosbuvir) that the virus thinks look the same as the one it needs it will use them and block the lock mechanisms stopping the replication from occurring.
So while we often think of the medication killing the virus sort of like a poison or something, it isn't really. It is just slowing its replication down enough for our immune systems to get back in control and do their job properly.
The side effects (which for
most people are fairly mild) are probably a combination of our immune system working hard and as you say the rapid viral die off plus the fact that anything new we add to our metabolism will have some sort of effect until we are used to it.
(Apologies to molecular chemists and biologists everywhere
)