There are several different pieces named Influenza Blues, most of them published in 1919. This particular piece is one of the better known titles, but it is neither legitimate blues, nor is it really about the flu. The song is about being so lonely that one might catch the flu if staying out too long in the rain.
Influenza Blues is from the 1919 musical A Lonely Romeo, which is best known for being the first musical to feature a song by Richard Rodgers and Lorenz Hart. The musical was received well at the time, and moved from the Shubert Theatre (still standing) to the Casino Theater (which was demolished in 1930). It had a successful five-month run.
Malvin Franklin himself was a prolific composer, not only of of musicals but also of film and stand-alone music. He was also a thermometer salesman.
Robert B. Smith started his career in vaudeville before composing operettas and musicals. He seems to be overshadowed, however, by his older brother, Henry B. Smith.
Key: Bb Major/Eb Major
Mood: surprisingly happy
Pedagogy: dynamics, repeats, first/second endings, syncopation