@Chris662
With illness you can come under the "extenuating circumstances" clause where you can contact airbnb and possibly cancel without penalties.
As for long term guests, that is another story. You either choose to do short term and possibly make more money (but there is also a lot more work involved) or you do long term. If you have taken bookings, you should honour them. Guests need reliable hosts, not hosts that cancel on them at random.
If you do not plan to list on airbnb in the future, go ahead and cancel. If you do plan to use airbnb in the future, that cancellation will count against you forever after.