fulminant: Descriptor for events that occur suddenly and escalate quickly.
Wikipedia
Fulminant is a medical descriptor for any event or process that occurs suddenly and escalates quickly, and is intense and severe to the point of lethality, i.e., it has an explosive character. The word comes from Latin fulminäre, to strike with lightning. There are several diseases described by this adjective: Fulminant liver failure Fulminant multiple sclerosis.
(Courtesy of Michael Kelly, H.W.)