Answer: FLU

Flu, short for influenza, is a contagious respiratory illness caused by influenza viruses. It is characterized by symptoms such as fever, fatigue, body aches, sore throat, cough, and nasal congestion. The clue "Apt rhyme of 'Achoo!'" suggests that flu is a word that sounds similar to the sound one might make when sneezing.

Note: The provided meaning of the answer is for the latest New York Times crossword puzzle clue: Seasonal threat. Explanations are generated by AI and may be inaccurate.