Candidiasis is a fungal infection (Candida albicans) that occurs mostly in the mouth and vagina (yeast infection). However, it does occur in other areas of the body, such as the skin or lungs. Candidiasis of the mouth (thrush) is the most common opportunistic infection in people with HIV. The chances of developing it increases as CD4 cell counts decrease. This is especially the case with CD4 counts below 200. Infection of the esophagus with Candida is the most common AIDS-defining condition and is more common in women than men.

Treatment of thrush is usually with topical medications (clotrimazole or nystatin) or with a pill such as fluconazole or itraconazole. If these do not work, even at higher doses, IV medications are often used, such as IV amphotericin.

Usually, higher CD4 levels will help keep Candidiasis from occurring, If, however, you ever had a very low CD4 cell count your CD4 cells may be less effective against Candida, even if the count has again risen above 200. Also, you may be more likely to get Candidiasis if you had it before. Your doctor may recommend that you use fluconazole or another anti-fungal medication regularly to prevent future flare-ups of Candidiasis.

The CD4 cells are very important in fighting infections as they help the immune system to recognize the invading organism (such as Candida) and tell special attack cells of the immune system to increase in number and go kill the invader. With a low CD4 count there are few messengers around to rev up the immune system to fight an infection.

CD8 cells primarily keep an eye on all of the cells of our body looking for any changes. When one of the body's cells is infected with a virus or becomes cancerous the outside of the cell changes and looks different. The CD8 cell can see this change and attack and kill the cell before more virus is produced or the cell grows more cancerous. CD8 cells are good at finding cells infected with a virus, but not very good at seeing other types of invaders. Other cells in the immune system, triggered by CD4 cells, are better at fighting fungal infections like Candidiasis. That's why people with low CD4 cell counts, but normal or high CD8 cell counts still get sick with opportunistic infections.

Heather Algren is an R.N., B.S.N. HIV Research Coordinator at Swedish Hospital and a STEP collaborator.