Hi everybody. Let me just jump right in. I have an on-going problem that I really need some outside perspectives on so I don't lose my mind.

My husband and I have 3 very young children together (the youngest being 1, the eldest being 6). He also has a child from a previous marriage. Due to the distance from each other, we see his child 1x a month, and then holidays. I have been in his child's life almost from the beginning, as they separated very early in the pregnancy, however, due to the very small amount of time we spend with him amongst other issues, I am not very bonded to him. I don't really have a step mother role, more of a caregiver/wife of his dad role, and that's okay- he has his own mom and I have no desire to try to push myself into that role.

Anyway, since my stepson was around 2, there has been a problem where every.single.time he comes over for any extended period of time, and about half of the time he comes over just for his monthly weekends, my entire household gets sick.

He himself often has a cough or congestion, but never is really sick or feeling bad. He is carrying some sort of germs that he is mostly immune to, but we get hit hard with without mercy. My eldest is in school, so we must be exposed to germs on the regular, but nothing gets us sick except my stepson. We are obviously not immune compromised because, like I said, we never get sick, except upon his arrival. But with his arrival inevitably comes illness. And I can not reassure myself anymore that we'll build up an immunity soon, because this has been going on for years, and very often we get sick with the same bugs over and over again (one in particular, which causes vomiting and extreme diareah can be identified by the abnormal smell of the poo before it even hits hard, so I know we've had this bug at least 15 times by now).

When it was just me and my husband, getting sick often was an annoyance, but tolerable. But I have three children of my own now, and it hurts me to see them hurting. To know that when my stepson visits, my poor babies will be throwing up, and/or sick with fever, and miserable within a few days... well, I am to the point where I dread his visits, and I am holding on to a LOT of resentment and anger, even if I know logically that he is not doing it on purpose. My daughter has missed so much school because of this that I now have to take her to the doctor each time she misses, or a truancy officer will be at my door.

When I see him sneeze and touch things, or go to the bathroom and not wash hands, etc. I am getting legitimately angry. And when I see him get near my baby, my first instinct is to run and scoop my baby up away from him. I know this is not a healthy or nice way for us to be together, but I feel I have developed a learned negative response to him, and I do not have any idea how to fix it. Sanitizing the house doesn't work. Pushing hygeine on him doesn't work. I don't understand how he can possibly be such a biological weapon, but dang, it is really not tolerable for me anymore. 

I write this, as we are on day 5 of a visit, and my 4 year old spent all night throwing up, and now my throat is scratchy, and it's all coming on AGAIN and I'm losing my mind. His last visit had the whole family knocked down vomiting every 15 minutes for 2 days. And it isn't just us. When extended family comes to visit when he is here, they get sick too. Two elderly family members have ended up hospitalized with severe illness immediately after visiting. One of them nearly died. I don't get what or why this is happening and I have no idea how to fix it. 

I need help, advice, anything.