Symptoms of flu Influenza (flu) is a contagious respiratory
illness. It can cause mild to severe illness and even death. The flu is different
from a cold. Flu symptoms come on suddenly and include9:
Fever
Headache
Tiredness
Dry cough
Sore throat
Nasal congestion
Body aches
Sometimes nausea, vomiting, and diarrhea
Differential diagnosis
for flu
The symptoms of cold and flu, when considered all together,
allow an empiric differential diagnosis.10 However a definitive diagnosis
of symptoms identified as flu requires laboratory testing.
