A cold is an inflammation of the tissues in the nose and upper airways often due to a viral infection. It often settles without any treatment. Flu (influenza) is a highly infectious condition often caused by viruses. While it involves the airways, it can quickly involve other parts of the body and can be severe in the very old or young. Sinusitis means painful swelling of the sinuses which are empty spaces around the cheeks, eyes or forehead. You may experience pain, tenderness or swelling in these areas.