WHAT ARE OPPORTUNISTIC INFECTIONS?

WHAT ARE OPPORTUNISTIC INFECTIONS?

In our bodies, we carry many germs – bacteria, protozoa, fungi, and viruses. When our immune system is working, it controls these germs. But when the immune system is weakened by HIV disease or by some medications, these germs can get out of control and cause health problems.

Infections that take advantage of weakness in the immune defenses are called “opportunistic”. The phrase “opportunistic infection” is often shortened to “OI”.
TESTING FOR OIs

You can be infected with an OI, and “test positive” for it, even though you don’t have the disease. For example, almost everyone with HIV tests positive for Cytomegalovirus (CMV). But it is very rare for CMV disease to develop unless the CD4 cell count drops below 50, a sign of serious damage to the immune system.

To see if you’re infected with an OI, your blood might be tested for antigens (pieces of the germ that causes the OI) or for antibodies (proteins made by the immune system to fight the germs). If the antigens are found, it means you?re infected. If the antibodies are found, you?ve been exposed to the infection. You may have been immunized against the infection, or your immune system may have ?cleared? the infection, or you may be infected. If you are infected with a germ that causes an OI, and if your CD4 cells are low enough to allow that OI to develop, your health care provider will look for signs of active disease. These are different for the different OIs.
OIs AND AIDS

People who aren’t HIV-infected can develop OIs if their immune systems are damaged. For example, many drugs used to treat cancer suppress the immune system. Some people who get cancer treatments can develop OIs.

HIV weakens the immune system so that opportunistic infections can develop. If you are HIV-infected and develop opportunistic infections, you might have AIDS.

In the US, the Center for Disease Control (CDC) is responsible for deciding who has AIDS. The CDC has developed a list of about 24 opportunistic infections. If you have HIV and one or more of these “official” OIs, then you have AIDS. The list is available at