I've had P. incense that had a virus. Maybe a mosaic type virus that makes the foliage develop yellow discoloration. I had them growing for several years near brugmansias and my brugs never developed a mosaic virus. I also have several salvia varieties though they weren't growing in close proximity to the incense. I have no idea if it remains in the soil or what other viruses affect passies.

Here is a link that might be useful: passie info