As soon as I threw the creep virus, the game started to freeze about 25 seconds out of each 2~3 seconds running.

Creep count was 368160, and it has been 30 minutes after I threw it, but it still freezes again and again.

I'll update this after the game stops freezing...

--Update1
It has been about an hour and the freezing time became 25sec to 22sec.... I see the progress!

--Update2
Schemed the source code (because I have enough time haha) and it seems it does not remove creeps enough, when the creep count is more than 40000.
Returning percentage of current creep count when creep count > 40000 from deincreaserPerIteration funtion may help, in my short think.

Thanks for your great mod, and have a nice day!

After editing and testing, I realized that I have misread the code.

First, I have modified deincreaserPerIteration to halve the biters, and the freezing just didn't end.
Maybe the random selection of creeps takes too much time.

After reverting it, I modified the first big replace procedure to reduce the creep count to near 40000 from any value, and the freezing became reasonable.

But it just instantly removes too many creeps, I couldn't witness the slow degrading of creeps.. :(

Unfortunatelly Factorio can't manage this as well, I have try different implementation, anyway is a one time thing...