“Loss of appetite and tiredness are symptoms that commonly occur together. Causes may include cold or flu”
https://www.medicalnewstoday.com/articles/loss-of-appetite-and-tiredness
Ah heck my momma told me all that when I was three. Influenzas can be killers though,,,obviously with high fevers, dehydration, and damage to kidneys and livers related to sepsis. You can have symptoms that are similar to both colds and flus if you have but one, but not the other.
It can be a drag if you are getting over a cold and you catch the flu...happened once to me.