He is suffering from a chronic disease.

I'm feeling down because of May sickness.

He was diagnosed with bipolar disorder and began treatment.

He got sunstroke because he was exposed to sunlight for a long time.

He is suffering from alopecia.

How does this pathogen infect humans?

My sick friend is fighting his illness with cheerfulness every day.

He is showing symptoms of catatonia.

His child is suffering from rickets.

My sister has celiac disease, so she can't eat foods that contain gluten.