Final answer:
Oral/esophageal candidiasis, or oral thrush, is a fungal infection caused by an overgrowth of the yeast Candida. It mainly affects individuals with weakened immune systems, such as immunocompromised individuals, patients with HIV/AIDS, patients undergoing chemotherapy, and patients with diabetes.
Step-by-step explanation:
Oral/esophageal candidiasis, also known as oral thrush, is a fungal infection caused by an overgrowth of the yeast Candida. This infection primarily affects individuals with compromised immune systems. The at-risk groups for oral/esophageal candidiasis include immunocompromised individuals, patients with HIV/AIDS, patients undergoing chemotherapy, and patients with diabetes. These groups have weakened immune defenses, making them more susceptible to fungal infections.