It's not accurate to say that a single organ is "usually" affected by fungus. Fungi can affect a wide range of organs and systems in the body, depending on the type of fungus and the individual's health. Here's a breakdown:

Commonly affected organs:

* Skin: This is the most common site for fungal infections, leading to conditions like athlete's foot, ringworm, and yeast infections.

* Lungs: Fungal infections can affect the lungs, causing conditions like histoplasmosis, blastomycosis, and aspergillosis.

* Nails: Fungal infections can cause nail discoloration, thickening, and crumbling.

* Mouth: Oral thrush is a common fungal infection that affects the mouth.

* Genitals: Yeast infections are common fungal infections that can affect both men and women.

Less common but important:

* Brain and nervous system: Some fungi can cause meningitis, encephalitis, and other serious infections.

* Eyes: Fungal infections can cause keratitis, a serious eye infection.

* Internal organs: In immunocompromised individuals, fungi can spread to internal organs like the kidneys, liver, and spleen.

Important notes:

* Immune system: The severity of a fungal infection often depends on the strength of the individual's immune system. People with weakened immune systems are more susceptible to serious fungal infections.

* Different types of fungi: Different fungi have different characteristics and affect different parts of the body.

* Symptoms: Symptoms vary depending on the type of infection and the affected organ.

If you suspect you have a fungal infection, it's crucial to consult a doctor for proper diagnosis and treatment.