Infections are defined by the type of organism involved and the location in the body. The most common organisms fall into three broad categories.

Bacterial Infections  A major source of these infections is bacteria normally found in our own gut (gastrointestinal tract). In a phenomenon known as sepsis, these organisms find their way into the bloodstream and can "seed" various organs.
    Bacteria on the skin can get into the bloodstream if an IV line is in place, resulting in sepsis or a local infection called cellulitis . A urinary catheter to drain the bladder can sometimes become infected and lead to a urinary tract infection. You may also have a greater chance of catching infections through social contact with people who already have an infection. A depressed immune system will make you more likely to acquire an infection in this way.
    Once any area of your body is infected with bacteria, the opportunity exists for bacteria to get into the bloodstream, spread and cause sepsis.

Viral Infections  When your cellular immunity is decreased, new viruses can take up residence in your body and old viral infections can be reactivated. Cold sores, for example, are caused by the Herpes simplex virus. This is a virus that stays with you, although it can have long quiescent periods. When your cellular immunity is damaged, the virus can flare up and give you quite severe cold sores. Another herpes virus—the same one that