Pyreticosis is not a commonly used word, but it refers to a fever or a condition that causes a fever. The spelling of this word can be broken down using IPA phonetic transcription. "Pye" is pronounced /paɪ/, "re" is pronounced /ri/, and "ticosis" is pronounced /tɪˈkoʊsɪs/. So the full pronunciation of "pyreticosis" is /paɪrɪˈkoʊsɪs/. This word may be difficult to spell at first, but breaking it down into syllables can make it easier to remember.
Any fever.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.