Influenza, or the flu, is a viral infection of the respiratory system. Symptoms of influenza often appear within a few days of being exposed to the virus. These symptoms typically begin 1–4 days after exposure to the virus and last for about 2–8 days. Influenza may progress to pneumonia, which can be caused by the primary viral infection or by a secondary bacterial infection.

Anorexia or loss of appetite

Nausea

Diarrhea

Sneezing

Nasal block

Rhinorrhea

Headache

Cough

Fatigue

Sore throat

Fever

Myalgia

Arthralgia

Influenza