A big thing is that Bats have a really weird metabolism, during their day it can dip down to 50 Fahrenheit and then go up to 104 F at night when they are active. This can mean they end up carrying a lot of diseases but not dying/showing symptoms of them. They also have very strong DNA repair compared to other mammals. Then in addition many bats are very social and sleep in big groups, which means the disease can spread throughout the bat population.

Edit: Finally and relevantly they can come in close contact with people by coming into our homes, or people going into theirs. This can let the disease cross over.

Not the OP, and my initial reaction was very similar. I'm giving the benefit of the doubt though and assume he meant monkeys in India will drink the naturally-occuring fermentation similar to how moose/elk in Scandinavia will get drunk on overly ripe fruit.

https://enviroliteracy.org/animals/can-elk-get-drunk/

Probably could have been a better choice of example than a monkey but if you spend a lot of time in India, the "we normally see these in a zoo!" novelty probably wears off quickly and its no different than dealing with deer in north america.