Most rabbits (the number is unknown but I've been told it could be as high as 90%) carry pasturella anyway. It is airborne so any rabbit in a multi-rabbit environment will likely have it, as they will catch it from the symptom-less carriers around them. Multi-rabbit environments would include breeders, rescues and pet shops... pretty much all the places rabbits come from. They don't get ill because their immune system keeps it in check. When the immune system is compromised for some reason e.g illness or stress, the bacteria gets a chance to multiply and 'flare up' and we see symptoms commonly known as 'snuffles'. Of course there are also other bacteria that cause 'snuffles' symptoms, but they are less common than pasturella.
None of your options really fit my experience of snuffles....Barney has chronic but mild snuffles. He was bonded with Annabella, who had been definitely exposed to snuffles - her father (who was kept with her mother, so she would have been a carrier) died from snuffles and she had also been kept at the rescue in the same barn/garage as a snuffle-bun. I don't think she was near the bun, but again, it is airborne. Annabella, when going through a very stressful time as the buns' bond was on the rocks, had a small episode of mild snuffles that lasted just over a week. She recovered with only a week of baytril but abx dont usually work that fast with snuffles, so I think her immune system managed it mainly. She has never *touch wood* had a reoccurance and is the healthiest bun I've ever met.