Urodelan flu is a relatively harmless viral disease. Symptoms include blurred vision, dizziness, palpitations, and a stinging sensation in the lower spine. Urodelan flu is characterized by a slightly irregular K-3 cell count, elevated intravascular pressure, and heightened electrophoretic activity. Some of these symptoms are similar enough to those of Terellian Death Syndrome that the medically inexperienced may confuse one for the other.

Most Humans are naturally immune to Urodelan flu. An exception was Reginald Barclay, who contracted it in 2370. Dr. Beverly Crusher attempted to cure it by activating the immunity gene with a synthetic T-cell, inadvertantly causing a condition later known as Barclay's Protomorphosis Syndrome. (TNG: "Genesis")