Sounds nefarious.
Was it Bill Hicks? who said the USA knew what chemical weapons Saddam had, because we sold them to him. We have the receipt!

Any military would definately keep an eye on biological weapons.
The usage of gas in WW1 by the Germans almost cleared the trenches had the Germans not hesitated. I don't think any political power/military/Govt can afford to be caught out weaponed.

The trading of weapons has always existed.

IRAN contra deal where you're selling weapons to your "enemy", French? I think, selling Nuclear parts/knowledge to "banned" countries.

I think contaminating the opposition with a virus, disease can cripple morale and fighting performance of your troops.

If an economy like China requires trade, was in a recent "Trade War", then has to close its borders due to a virus - alot of fiction can be written about that.