animals can carry bugs.  my wife has autoimmune diseases including sjogrens and hashimotos.  its very tough.  she can and usually will catch any sickness anyone around her that anyone has.  she has to get infusions to raise her immune system once a month.  i would have as much patience as possible as long as she is contributing something.  sometimes low immune system people need to work from home but not sure if thats possible in your case.