Published: 18 Jun 2025

ICD9: 487.0      ICD10: J11.0      ICD11: 1E32

"Influenza," commonly known as the "flu," is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and lungs.
It can cause mild to severe illness, and at times can lead to death.

Here's a breakdown:

Cause: Influenza viruses (Type A, B, and C, with A and B being the primary cause of seasonal epidemics).
Transmission: Mainly through droplets made when people with the flu cough, sneeze, or talk. These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs. Less often, a person might get the flu by touching a surface or object that has flu virus on it and then touching their own mouth, nose, or eyes.
Symptoms: Common symptoms include:
Fever
Cough
Sore throat
Runny or stuffy nose
Muscle or body aches
Headaches
Fatigue (tiredness)
Some people may have vomiting and diarrhea, though this is more common in children than adults.
Complications: The flu can lead to serious complications, including:
Pneumonia
Bronchitis
Sinus infections
Ear infections
Worsening of chronic medical conditions (e.g., asthma, heart disease)
Prevention: The best way to prevent the flu is by getting a flu vaccine each year. Other preventive measures include:
Avoiding close contact with sick people
Washing your hands often with soap and water
Covering your cough or sneeze
Treatment: Treatment options include:
Rest
Fluids
Over-the-counter pain relievers and fever reducers
Antiviral medications (prescription drugs that can shorten the duration of the illness and reduce the risk of complications, especially when started early)

In short, the flu is a common but potentially serious viral infection that affects the respiratory system. Getting vaccinated and practicing good hygiene are key to prevention.