I suggest you have a read of this:
Can certain vitamins and minerals keep your immune system at its best? Yes! A registered dietitian explains how.
health.clevelandclinic.org
Over the last 40 years, I have read a lot about nutrition and supplements. One supplement which I recently found interesting is monolaurin. It is contained in human breast milk for protecting the new born baby from viral infections. It's found in coconut milk and also available as a supplement. IMO, there's no risk in trying it. There is some info on the web on it and Amazon sells it.
That is my 2 cents.
I wish a prompt recovery to your wife. Have a good day!