It is good that you want to make sure your daughter feels no responsibility for your reactions. I agree with Nicolette, children are very perceptive. They also often need less information than we might think, but it's important to be cautious about how they "fill in the blanks" in their heads. You can probably bring this up during a 'teachable moment' in your daily life. It seems important to say that
1. It's not her fault and she hasn't caused you to feel ill or worsened your illness; and
2. That you are taking care of yourself and will feel better soon, so she needn't do anything.

Five is still very young and what she's probably most worried about is being 'bad' by causing you to feel ill and that her security and safety will be affected. Reassurances to the contrary, and seeing you take responsibility for healing, will go a long way in managing things.