Please tell people if someone attending an event is sick!

Okay so this past weekend I was spending time with my partners extended family. It was already a draining weekend, but fun nonetheless. There is a small child in the family who for some reason was obsessed with me and wanted to hang out with me non stop (i’m not sure why this always happens, I am not a fan of kids but they seem to like me a lot) who was sick. I was not informed by the parents, but rather in an offhand unrelated conversation with another family member that she was sick. I had watched this child cough all over me and my food all night thinking well ya know kids are gross and they cough but it’ll be fine. As an immunocompromised adult I get ill very quickly. In the four hours that this child was by my side I have caught what she has and am now unable to function. My partner is very upset with his family for no one informing me that she was ill because we would have approached the event very differently. This has happened many times now, if someone at an event is ill please tell the others. Or if you are ill and going to spend time with others please let them know so they can adjust and plan accordingly.