5 year old sick nephew problem

My husbands sisters son is apparently sick the drs said he has the flu. I understand kids get sick but what I don’t understand why do mothers believe it’s ok to not teach their kids to cover their mouth when they are coughing. Her son literally coughs around everywhere with his mouth wide open to the point he got my son sick. And none of my in laws believe me when I say that he got my son sick. They said only god can get people sick. I am truly religious but come on there’s just some things that are common sense. There are sickness that are contiguous. Like coughing hard without covering your mouth, that’s germs spreading. I got the cold from my husband this one time just from kissing him on the lips like a innocent kiss and taking care of him when he was sick. my in laws sound crazy asf. But what I’m mad about is I been told the 5 year old to “close his mouth, there’s a lot of people in this house including a newborn, who will get sick because of you”. I told him that in front of his mother who is my sil and the Aunty of my son. She told her son “Tell her we don’t care” which threw me off the roof because that’s basically saying you don’t care who your son gets sick? Than I went back to school and my husband asks his sister if she can watch our son till he gets back from dropping me off at school. Just from being in that room, my son got sick. Sickness just doesn’t happen right away it takes few days or few weeks to kick in to the immune system. With that being said my sil wanted to complain and get mad at me from keeping my son away from her room. She wanted to tell my parents in law that I am trying to keep her nephew away from her because he was in her room for a while, and just all of a sudden he is sick. Blah blah blah they believe in HIV being contiguous by having sex but don’t believe germs are contiguous by coughing, touching etc? So even since we got into the argument because I told her her son got my son sick, she kept her distance from my son by her own choice but telling people that I’m keeping him away from her which I’m not she can hold him and play all she wants but he isn’t going into her room where she allows her son to cough without closing his mouth. Now it’s been like since October? That my son been sick. He has a hard cough just like the nephew. My son was diagnosed with broconvirus, I don’t know how to spell it lol. He has bad wheezing, his wheezing has gotten worse. He can’t breathe right because his nose all stuffy. When you listen to his lungs, it sounds junky. I took him to a lot of appointments I even took him to the ER they didn’t do nothing but charge us money. All they said was go to his primary care. He doesn’t have a specific dr. We just go to a clinic. All the clinic gave him was breathing treatments, and medicine to make his boogers watery so they can come out. None of them helped. I tried everything and they can’t give him a antibiotic because it’s a virus. It’s been months now and my son still sick. The drs said it should go away in couple weeks. But it’s been months and the sil doesn’t even ask how my son doing or nothing. She be hearing him cough hard way too hard for a 5

Month old but she ignores it. She doesn’t even look like she feels bad, like she didn’t thought it over and asked herself what if my son did get him sick? What kind of aunt ignores her nephew just to be petty to the mother? We currently live with them, husband saving up enough money to move out and as soon as I move out, I am never going back to my in laws house ever again. All they do is make me look like the bad guy all the time. I am currently pregnant again and haven’t told any of them. I asked my husband to keep it quite and he agreed with me. They don’t need to hear about our second baby since they don’t even care about the first one. My question is was I wrong to say that to her? Because they really making it look like I’m starting problems.