Are bacterial infections contagious?

Not the "infections": All bacteria are contagious, meaning that one person can smear some of his bacteria onto another's skin or other body part. The bacteria can then die, multiply on the surface (colonize the surface), or damage the person's cells and body parts (start an infection). No infection occurs in many cases, meaning the "infection" did not spread to the person even though the "bacteria" did spread to him.

Technically correct: While dr. Kwok's answer is exactly right, the practical answer is yes. Bacterial infections can be passed from one person to another, and are therefore contagious. It is possible, however, to come in contact with a bacterial infection and not catch it.

Not the "infections": All bacteria are contagious, meaning that one person can smear some of his bacteria onto another's skin or other body part. The bacteria can then die, multiply on the surface (colonize the surface), or damage the person's cells and body parts (start an infection). No infection occurs in many cases, meaning the "infection" did not spread to the person even though the "bacteria" did spread to him.

No: No. Some are and some are not.

Sometimes: Some bacterial infections are, like strep throat, or pink eye, but many develop that are not really contagious, like sinusitis, cellulitis, or diverticulitis. If you have a concern, you should discuss the specifics with your doctor. It is also always a good idea to always wash your hands or use hand sanitizer, whenever you are out, like shopping, airports, grocery stores etc to minimize risks.

Some are/some not: Some bacterial infections like Meningococcal meningitis and tuberculosis are contagious. Others like an e. Coli urinary tract infection or a ruptured appendix with peritonitis are not.