Worldwide, bacterial infections are responsible for more deaths than any other cause.
Symptoms can include inflammation and swelling, pain, heat, redness, and loss of function.
The most important risk factors are burns, severe trauma, low white blood cell counts, very old or young patients, patients on immunotherapy treatment, and anyone suffering from malnutrition or vitamin deficiency. Bacteria are generally spread from an already infected person to the newly infected person. The most common invasion routes are inhalation of airborne bacteria, ingestion into the stomach from dirty hands or utensils or through contaminated food or water, direct contact with an infected area of another person's body, contaminated blood, and by insect bite. The first of the body's three primary lines of defense includes naturally occurring chemicals such as the lysozymes found in tears, gastric acid of the stomach, pancreatic enzymes of the bowel, and fatty acids in the skin. The body's immune response becomes involved only if the infective organism manages to invade the body.