This page contains information regarding Star Trek: Lower Decks, and thus may contain spoilers.
Terellian Death Syndrome was a deadly disease which caused cellular decay. Its initial symptoms were somewhat similar to that of Urodelan flu, and included blurred vision, dizziness, palpitations, and a stinging sensation in the lower spine.
Captain Carol Freeman came down with Terellian Death Syndrome in 2381, which was cured by Ensign Escher. According to Ensign Sam Rutherford, Escher "was in the right place with the right hypospray." (LD: "We'll Always Have Tom Paris")