There aren't many infections which would be more evil than RHD and RHD2 for rabbits.
How can they spread?
I did some research on the Internet and it turns out that RHD (rabbit hemorrhagic disease) is a viral disease with extremely high infectiveness and many various potential routes of spreading.
At first, some clarification. RHD is the acronym of the disease itself, and it is caused by rabbit hemorrhagic disease virus (RHDV), of which two different strains are considered:
RDHVa, also referred to as RHDV, RHDV1, or as classical RHD. It only affects adult European rabbits (Oryctolagus cuniculus).
RDHV2, also abbreviated as RHDV2 or RHDVb, distinctive genetic, antigenic, and pathogenic features. It was identified in France relatively recently, in 2010. It novel properties were manifested in the fact that it killed rabbits previously vaccinated with RHDV vaccines. What is more, it affected young European rabbits, as well as hares (Lepus spp.).
As for the transmission routes of these pathogens - it could occur:
Aforementioned versatility of transmission routes means that rabbit could also spread the disease or become infected by contact with fomites - like for example water bowls, bedding, food, etc. What is more, surviving rabbits may be contagious for up to 2 months.
Also, the virus itself is highly resilient and could remain infectious outside of the living host for up to three months (within infected rabbits' carcasses and meat). It is also told to be resistant to prolonged periods of freezing.
My sources were: