Colds are caused by viruses and easily spread to other people. You're infectious until all your symptoms have gone. This usually takes a week or 2. Colds are spread by germs from coughs and sneezes, which can live on hands and surfaces for 24 hours.

A cough is a reflex action to clear your airways of mucus and irritants such as dust or smoke. It's rarely a sign of anything serious. A "dry cough" means it's tickly and doesn't produce any phlegm (thick mucus). A "chesty cough" means phlegm is produced to help clear your airways.

Flu is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and sometimes the lungs. It can cause mild to severe illness, and at times can lead to death. The best way to prevent flu is by getting a flu vaccine each year.