Hay and RHDV
The answer here, as practiced by those in the UK and EU where RHDV2 is endemic, is to buy far ahead of your need, and quarantine your hay for FOUR MONTHS, not less. That means no bugs, no birds, no rodents, no contact by anything if at all possible.
For pet owners, this should be relatively simple. Disinfect the outer packaging (make sure it doesn't have holes and be careful if it does) and store in a dim, well ventilated area.
There is no such thing as hay that is grown without any possible exposure to RHDV in an area where it is present in the wild population, so it's much better to be safe than sorry.
Admin for FB groups
North Americans RHDV2 Group
RHDV Information Page
Supporting the RHDV Vaccine in the US