@Christopher1016
No Christopher. It is not reasonable to expect your Host to provide a full refund.
Your parties health is no fault of your host and provides no reason why the rest of your party cannot travel. Continue your trip and leave your ill friend behind (if at that time they are still ill of course). Alternatively, claim on your travel insurance. Thats what its there for. Should you wish not to travel because of the illness of your friend, cancel and expect to pay the full cancellation fees of your host and the full service fees of Airbnb. That is all in your contract.
If you wish to reschedule your trip, I'm sure that your host will try to accommodate you any way they can.
I would expect that making any cancellation pivotal on the illness of any particular guest would need to have that guests' details fully disclosed and identified to the host before attempting to obtain a refund based on that person's inability to travel.