There is no difference in the illness caused by the two serogroups.

两种血清性引起的疾病症状没有区别。

There are many serogroups of V. cholerae, but only two – O1 and O139 – cause outbreaks.

霍乱弧菌有许多血清型，但只有O1和O139两种血清型会引起霍乱暴发。