I see what you're getting at, but a virus that can infect everyone and easily spread is impossible to use in any sort of directed way. A student could easily catch it from another student at school, then go home and infect their father, who may be an older high-ranking CCP official, for example. It does way more than discourage large gatherings, kills pretty indiscriminately (beyond some factors like age and history of smoking), and of course is a massive hit to the economy and society as a whole. And it'd also be very likely to spread to the rest of the world.
It'd be like trying to deal with overpopulation by setting a computer program to randomly select 20 of your own population centers to nuke, then launching nukes. Then a week later choosing other random cities around the world to nuke. Plus, it'd probably be discovered eventually, and would obviously be the most severe pre-emptive act of war ever known. It would inevitably cause WWIII, leading to much more death and chaos. It's a completely illogical and self-destructive strategy.
Now, if it were a virus that, say, couldn't infect those with a gene found in all Han Chinese people, and which isn't found in any other groups, that would be worthy of some investigation. Or only infected Uyghurs.
I know this is just playing Devil's advocate, but I think the odds are so low as to essentially be zero, unless the CCP has some sort of bizarre motivation that's extremely distant from nearly everyone else's motivation (like trying to end the world and make humans extinct).