The sentence "Stay safe; stay well; stay hydrated; stay curious." employs the rhetorical device known as anaphora. Anaphora is the repetition of a word or phrase at the beginning of successive clauses or sentences. In this case, the phrase "stay" is repeated at the beginning of each clause, creating a rhythmic and emphatic structure that reinforces the message.
This device is indicative of anaphora because the repeated element ("stay") creates a sense of urgency and importance around each of the ideas presented (safety, wellness, hydration, curiosity), enhancing their significance in the reader's mind.