MedDroidFlu vs Pneumonia
Flu vs pneumonia: differences in symptoms, tests and treatment
Written & medically reviewed by Dr. Sanjay Anbu, MBBS · Last reviewed
Medically reviewedFlu is a viral infection of the nose, throat and airways; pneumonia is an infection deep in the lungs' air sacs, which can be caused by bacteria, viruses or fungi. Pneumonia can follow flu. Breathlessness, fast breathing and chest pain on breathing are signs that it may have become pneumonia and need prompt medical review.
Side-by-side comparison
| Feature | Flu | Pneumonia |
|---|---|---|
| Cause | Influenza A or B virus | Bacteria (often pneumococcus), viruses (including flu) or, less often, fungi infecting the lung air sacs |
| Typical symptoms | Sudden fever, body ache, dry cough, sore throat, tiredness | Cough often with phlegm, fever, fast or difficult breathing, chest pain when breathing in, tiredness |
| Onset & timing | Starts suddenly; most people improve in about a week | Can develop over a few days, or after flu seems to be getting better |
| Key tests | Usually diagnosed on symptoms; flu test if needed | Doctor listening to the chest, chest X-ray, oxygen level (pulse oximeter), CBC, CRP |
| Treatment approach | Rest, fluids, fever control; antiviral medicine for some people | Antibiotics if bacterial; oxygen and hospital care if oxygen is low or illness is severe |
| Danger signs | Breathlessness or chest pain suggest a complication | Low oxygen, confusion, bluish lips, very fast breathing, low blood pressure |
General patterns only. Symptoms overlap and vary from person to person. On a phone, scroll the table sideways to see both columns.
How doctors tell them apart
- Breathlessness and fast breathing are more typical of pneumonia.
- Doctors listen for crackles in the lungs and may order a chest X-ray.
- A low oxygen reading strongly suggests lung involvement.
- Blood tests like CBC and CRP help judge how severe the infection is.
See a doctor urgently if
- Breathlessness at rest or fast breathing
- Oxygen reading below about 94%, or as your doctor advised
- Chest pain when breathing
- Confusion or bluish lips
- In children: chest drawing in with each breath, or not feeding
In an emergency, call your local emergency number (in India: 108 or 112).
Frequently asked questions
Can flu turn into pneumonia?
Yes. Pneumonia is one of the most common complications of flu, especially in older adults, young children and people with long-term illnesses.
Is pneumonia contagious?
The germs that cause it can spread through coughs and sneezes, though not everyone exposed gets pneumonia.
Do I always need a chest X-ray?
Not always, but it is often used when pneumonia is suspected or when symptoms are not improving.
Are there vaccines?
Yes. Flu and pneumococcal vaccines lower the risk of pneumonia. Ask your doctor whether you need them.
Related pages
Conditions
Symptoms
Blood tests
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Not a diagnosis. This page gives general health information to help you talk to a doctor; it is not medical advice and does not replace an examination or tests. Do not start, stop or change any medicine without a qualified clinician. MedDroid is an AI medical assistant and can make mistakes. In an emergency, call your local emergency number (in India: 108 or 112).