What common condition is caused by viruses and affects the skin?

Warts are caused by human papillomavirus (HPV) and are a common condition that affects the skin. These benign growths can appear anywhere on the body and are contagious, spreading through skin-to-skin contact or contact with contaminated surfaces. The virus triggers an overproduction of skin cells, leading to the characteristic rough texture and raised appearance of warts.

In contrast, the other options refer to different causes or conditions. Fungus is a type of microorganism that can cause various skin infections, but it is not a condition itself. Dermatitis is inflammation of the skin with various potential causes, including allergies and irritants, and is not primarily viral. Psoriasis is an autoimmune condition that causes rapid skin cell production leading to scaling and inflammation, and it is not caused by viruses. Thus, warts stand out as the correct answer due to their clear association with a specific viral infection.