And the mode of transmission is ....?
You take your chances with it if you like. I, for one, prefer the legal system's requirement of at least a minimal standard of healthiness and vaccinations for each immigrant as a precondition for admittance into these United States.
IMO, those who steal their way into the US and are discovered carrying disease ought be treated as though they would be carrying deadly weapons and prosecuted likewise, with their host country billed for care and/or incarceration.
Unfortunately there is no way to diagnose leprosy before it becomes symptomatic -- usually 4-6 years after infection, but sometimes as long as 20 -- and no vaccine. TB and polio are much easier to detect and there is an effective vaccine for polio, so those diseases can be the subject of immigration laws. But not leprosy (which isn't a problem anyway, with only about 100 cases a year in the U.S.). Worrying about TB and polio is well-founded, but when you hear someone babbling about the threat of an immigrant-caused leprosy epidemic, you can be confident that the speaker is clueless on the subject of public health.