Opportunistic infections are so named because they occur in people whose immune systems are not working properly; they are "opportunistic" insofar as theinfectious agents take advantage of their hosts' compromised immune systems and invade to cause disease.
The organisms that cause opportunistic infections are categorized as protozoa, fungi, viruses and bacteria. These organisms are found widely in nature andoften live in the human body. When the immune system is working properly, itcan control the germs. However, persons with defective immune systems are unable to fight off the growth and destructive action of these organisms withinthe body. Opportunistic infections are seldom spread to people who have normal healthy immune systems.
One of the ways the immune system can be damaged is when the person is infected by HIV. In addition, drugs used to treat cancer, and drugs used to facilitate organ transplants can also suppress the immune system.
A person infected with HIV can get an opportunistic infection, when the counts of a particular immune cell (T cell) in the blood falls below a certain critical number. The most common opportunistic infections that an HIV-infected person get are Candidiasis or Thrush, Cytomegalovirus, Herpes simplex virus, Mycobacterium avium complex, Pneumocystis carinii pneumonia, Toxoplasmosis, and Tuberculosis.
Most of the germs that cause opportunistic infections are quite common. One can reduce the risk of infection by keeping clean, having hygienic practices,and avoiding known sources of infection. Diagnosing an opportunistic infection can be very tricky. Generally, the symptoms are rather vague and non-specific and could be due to a multitude of factors. Hence, the physician has to order blood culture and other laboratory tests to make a definitive diagnosis.Even if an immuno-compromised person gets an opportunistic infection, there are medications that will prevent active disease. This is called prophylaxis.Getting vaccinated against pneumococci, a leading cause of bacterial pneumonia in the immuno-compromised people, is now recommended by the Ntaional Institutes of Health.
Because of the AIDS epidemic and the mortality associated with it, a lot of money and effort has been expended in the past decade on research aimed at theprevention and treatment of opportunistic infections. Much progress has beenmade and currently, there are specific drugs or combinations of drugs that seem to work best for each infection. Many researchers are also of the opinionthat if a person's damaged immune system can be rebuilt, he will be better protected against opportunistic infections. When people use the newest drugs that fight HIV, its possible that their immune system can repair some of the damage done by HIV, and can do a better job of fighting opportunistic infections.