Advice on step son being sick all the time.

Okay, so, I need helpful advice on the current situation I am in. My step son is with us over night's on Wednesdays and then every other weekend. The schedule is a little different for summers, spring break, etc. But, while I love having him here, his mother is not the cleanest person in the world. She has two kids both younger than him (he is 8, his brother is 3 and his sister is 1 and a half). Because she does not take cleanliness as a priority, my son has brought home 5 nasty bugs in the last 2.5 months to my daughter. She's had three ear infections, a cold, and this week a bout of the stomach flu. The doctor tells me if she has one more infection in the next month or two she will need tubes. She is also battling low iron, and doesn't feel the best already from that.I don't want my daughter going through all this because my husband's ex can't keep her kids healthy. I know that might sound bad, but I do love my step son. It just hurts me to see my daughter going through all this for a few hours of visitation. My step son is literally always sick. From October to April he's sick every two weeks. After bringing home the flu last week, he now has another cold.Has anyone else gone through a similar situations with step kids? What is your advice on how to deal with it all? Is there a way you've kept your own kids from getting sick as much? Or do you just let things be and hope for the best?Thank you via /r/Parenting http://ift.tt/2n6AxIa