Sometimes you get sick just like anyone else, but unlike children or other healthy adults who can recover quickly if they happen to catch your illness, elderly people recover slowly, and possibly with serious complications. This is especially true if the elder has a chronic respiratory weakness (as Mom does here).
So what to do about it? Other than the obvious thing of having separate kitchen times, consider wearing disposable gloves in general and a simple dust mask when you are in the unavoidable situations where you have to be in talking distance of each other. I also wipe down all surfaces that I touched with disinfecting wipes and spray disinfecting aerosol in the breathing space we both pass through. Both the wipes and the sprays are available at low cost in a variety of pleasant scents. The masks are available at hardware stores in multi-packs, and gloves can be purchased at medical supply stores.
Yes, it is an extra hassle when you are already hassled by being ill, but better to be cautious than trying to deal with a situation.
Mom went through a rough stretch the past several weeks. During this time she had oral surgery to remove a tooth, extreme upper back pain (which we though was yet another broken vertebra), and a secondary lung infection that produced the most vicious cough you could imagine.
This meant extra work for myself and my local sibling, including for example, working new medications into the rotation in way that does not conflict with other established medications or regular food meal selections (some diary and vitamins interfere with antibiotics).
On top of all of this, one of my two outside care providers was on a 3 week trip/absence, so I had to pick up the hours myself.
As of today, it appears that the tooth and back issues are fully resolved, and the cough is about 75% gone. What a short-term whirlwind that was though!
Now you can begin to sense that care giving does not follow a recipe; it involves trade-offs so that you can never fully win at all times. Sometimes issues arrive unexpectedly and concurrently, and then some of your own lifestyle choices need adjustment.