The two pathogens we detect most frequently in African Violets and other gesneriads are Impatiens necrotic spot virus and Tomato spotted wilt virus. Both are transmitted by thrips and can cause a number of symptoms, which can include ringspots and mottle on leaves and brown rings around the leaf petiole. Other viruses can also cause mottled patterns, as well as symptoms such as distorted leaves.
One other virus we often find in African Violets is tobacco mosaic virus, which can be transmitted by people handling plants, by plant-to-plant contact, or in soil. Watering with cold water can produce spots and rings that resemble virus symptoms.