Viruses that spread readily suck as biological warfare agents. Even if you don't care all that much about your own people, the risk of Chaos is much too great.

Viruses that spread readily suck as biological warfare agents. Even if you don't care all that much about your own people, the risk of Chaos is much too great. Nobody can contain such a virus, and China didn't come out ahead, nor did it expect to. Its export markets suffered a great deal, and at the beginning it was far from certain that China could contain the domestic damage as well as it did.