I wish especially to call attention to two features of this depression, for I do not know that they follow any other disease, so I regard them as the most remarkable and probably the most important of any of the phenomena that are associated with influenza. These features are the subnormal temperature and the reduced pulse-rate. In the cases of which I have kept records, the temperature ran from 97 to 95 F., and the pulse from 60 to 48, for weeks and months. This is most characteristic of the disease, and it strikes me as most strange that it has not been described. I have read over the works of Osler, Wood, Fitz, Lyman, Whittaker, Struempell, Tyson and Pepper, and none of them speak of this subnormal temperature and reduced pulse-rate which, I have noticed, follow influenza.
Tyson says: "Weakness following influenza may be extreme, and the slightest effort,
BYRNE BJ. NERVOUS DEPRESSION AS A SEQUEL OF INFLUENZA.. JAMA. 1900;XXXIV(10):596–597. doi:10.1001/jama.1900.24610100018001e