I think it's because none of them really get sick so they weren't noticing any signs. That or yeah they didn't pay enough attention lol
I don't think they were ignoring him, because they really seem to care about him. What happens is that Seth, Horus and Jesus (lol) are obviously super strong and not easily hurt, they probably just forgot about humans being this weak. The guy has been really helpful for them 3, so they kept him around also so he doesn't die. It's like if you have a fish and had only cats as pets you're not going to know how to take care of it
Did anyone else think that : I thought it weird that the human has been looking sick for some chapters now and they didn't say nothing or try to help him sooner . It was kind of weird. You can tell he was getting sicker I didn't know what that was suppose to mean because they were just ignoring him?