Postpartum Psychosis is a rare illness, compared to the rates of postpartum depression or anxiety. It occurs in approximately 1 to 2 out of every 1,000 deliveries, or approximately .1 -.2% of births. The onset is usually sudden, most often within the first 2 weeks postpartum.
I know one is to get tested. Another could be to use protection that could prevent that kind of stuff. Then if you're already infected, you should tell your partner. And if you do sleep with your partner while infected, tell them to get tested.