An exotoxin is a toxin secreted by bacterial cells. These toxins can be attacked by a person's immune system, unless they are too fast acting in which case the toxin may cause death to the host. An example is the botulism toxin caused by Clostridium botulinum. This bacteria is found in soil and the spores can be killed by washing or properly cooking fruits vegetables. However, when home canning is done, if food is improperly canned, this can result in food tainted with botulism. The toxin affects the nervous system and can result in respiratory failure and death. Diptheria, which was once a deadly disease, is due to bacteria that secrete toxins that can do respiratory and heart damage. Due to DPT vaccines given during childhood, diptheria is fairly rare in the U.S. Exotoxins once released either by secretion or lysis of the bacterial cells can cause death to the host cells or disrupt the host cell's normal metabolic activity.