What Causes Opportunistic Infections? OIs are caused by a variety of germs (viruses, bacteria, fungi, and parasites). These germs spread in different ways, such as in the air, in body fluids, or in contaminated food or water. They can cause health problems when a person's immune system is weakened by HIV disease.

What is the main feature of an opportunistic infection?

Opportunist organisms have three main characteristics: (1) they are usually organisms of low pathogenicity, (2) they cause serious infections mainly when the host's defense mechanisms against infection are impaired, and (3) they can behave as conventional pathogens but under opportunistic conditions may cause atypical ...

How can opportunistic infections be prevented?

Don't eat foods such as undercooked eggs, raw (unpasteurized) milk or cheese, unpasteurized fruit juices, or raw seed sprouts. Don't drink water that may not be clean, such as from lakes and rivers, or when traveling to foreign countries. When in doubt, use bottled water. Take care around animals.