MODEL RELEASED. Oral thrush. Close-up of the mouth of a 48-year-old man who is HIV positive and has a candidiasis infection (white areas) affecting his mouth. Candidiasis, known as thrush, is an infection by the fungus Candida albicans. Patients with HIV (human immunodeficiency virus) can develop AIDS (acquired immune deficiency syndrome) and become immunosuppressed, leaving them open to secondary infections.