When the flu (influenza) leads to Pneumonia
Battling the flu can tax your immune system and increase the chances that you'll develop pneumonia. To help prevent other infectious organisms from gaining a foothold in the lungs, drink lots of liquids. Avoid taking antihistamines, which can dry and thicken secretions in the respiratory tract. Also, try to avoid smoking and drinking excessive alcohol, which can interfere with the body's natural mechanisms that flush out invading organisms. Taking these simple precautions can help you recover from the flu and help prevent pneumonia and other illness. - American Lung Association
| Symptom | Cold | Flu | Pneumonia |
| Fever | Rare | Characteristic, high (over 101 F) lasting 3-4 days | Characteristic, high and rises rapidly (up to 105 F) |
| Headache | Rare | Prominent | Generally no |
| Muscle aches and pains | Slight | Usual and often severe | Occasionally |
| Fatigue | Mild | Early, prominent and can last up to 2 to 3 weeks | Occasionally |
| Stuffy/runny nose | Common | Sometimes | Generally no |
| Sore, scratchy throat | Common | Sometimes | Generally no |
| Chest discomfort/pain | Mild to Moderate | Common | Common |
| Cough | Common | Generally a dry hacking cough | Moist cough; may produce rust-colored sputum or pus |
| Onset of Symptoms | Gradual | Rapid | Gradual |