How can I tell if I have the common cold (with bronchitis), flu or pneumonia?

Not so easy. Pneumonia is an infection of the lung or lower respiratory tracts. A cold (usually caused by viruses) is an infection of the upper respiratory tract - flu also usually affects the upper tract but can start involving the lungs (serious). A patient should see a physician who can do lab tests and get an x-ray - doubly important to do so if a person is getting worse, dehydrated, or short of breath.

Related Questions

How do I know if I have a cold or flu? How can I tell if I got the common cold, influenze or pneumonia?

A cold is. Usually an upper tract issue, ie clear nasal discharge and congestion. Flu is associated with more systemic symptoms including fevers and muscle aches. Pneumonia by definition involves infection of the lung itself and can be confirmed by physical exam and chest xray. Read more...
Flu worse than cold. A "cold" is an upper respiratory infection. It is usually associated with a stuffy nose and sometimes other symptoms related to that (post-nasal drip leading to cough, headache due to sinus congestion, etc.) a flu has an associated fever (increased body temperature), muscle aches, feeling bad all over. Pneumonia means you have a bacterial or viral infection in the lung. Read more...