While it is a really good anti-parasitic, it looks like the reason why it's useful in regards to the chinese flu (and other viruses) is that it acts like a protease inhibitor.

It might not be a full blown protease inhibitor, but it does seem to block a specific enzyme 'CYP3A4'. Interestingly hydroxychloroquine and grapefruit also block this enzyme (that's why some medicines have warnings against grapefruit usage). I am sure there is a laundry list of other things that also potentially block this enzyme.

The new drug coming out, paxlovid, now has similar side effects and warnings as protease inhibitors (ie don't take with statins, blood thinners, changes in insulin levels). This signals that the path "they" are going seems to be pointing towards widespread use of protease inhibitors as a therapudic. (which will have its own difficulties but that is another story)

tl;dr An enzyme (maybe CYP3A4) or process is being blocked, preventing the virus (and likely other things good and bad) to not be able to replicate/reproduce/function and thus not be able to spread.

^correction: I may be wrong about HCQ blocking cyp3a4 enzyme, it does block an enzyme(s) but it might be a different one. the above conclusion still seems appropriate though.

While it is a really good anti-parasitic, it looks like the reason why it's useful in regards to the chinese flu (and other viruses) is that it acts like a protease inhibitor.

It might not be a full blown protease inhibitor, but it does seem to block a specific enzyme 'CYP3A4'. Interestingly hydroxychloroquine and grapefruit also block this enzyme (that's why some medicines have warnings against grapefruit usage). I am sure there is a laundry list of other things that also potentially block this enzyme.

The new drug coming out, paxlovid, now has similar side effects and warnings as protease inhibitors (ie don't take with statins, blood thinners, changes in insulin levels). This signals that the path "they" are going seems to be pointing towards widespread use of protease inhibitors as a therapudic. (which will have its own difficulties but that is another story)

tl;dr An enzyme (maybe CYP3A4) or process is being blocked, preventing the virus (and likely other things good and bad) to not be able to replicate/reproduce/function and thus not be able to spread.