How dangerous is touching leprosy patients?

Not much. Most persons who acquire leprosy do so after long term intimate contact. Transient contact is not likely to produce transmission, but as my mentor used to say "never say never".
Leprosy. has been called the least contagious of the infectious diseases. One may carry these bacteria for five to 20 years before becoming symptomatic. About 95% of people have natural immunity to Leprosy. It is most likely that leprosy is transmitted by nasal droplets.