Well I've been keeping regular rats for over 4 years, ASF's for over a year. Far as I know I'm not dead yet.

All joking aside, if you use common sense you should be fine. Buy your breeding stock from a good source so you aren't bringing in nasty rats from a nasty rat breeder. Feed them well. Provide drinking/sipping water bottles not drinking bowls. Use rat safe bedding for them (no cedar or pine products). Clean them on an appropriate schedule for the size of enclosure and the number of animals it holds so your breeders/feeders aren't sitting on urine and feces soaked bedding. Provide reasonable ventilation both in the enclosures and the room that holds them. Remove and isolate any obviously ill rat from the general population. Wash your hands after you work with the rats. Just use basic good sense husbandry methods.