Mumps, also known as epidemic parotitis, is a viral disease caused by the mumps virus. Initial signs and symptoms often include fever, muscle pain, headache, and feeling tired. This is then usually followed by painful swelling of one or both parotid glands. Symptoms in adults are often more severe than in children. About a third of people have mild or no symptoms. Complications may include infections of the covering of the brain (15%), pancreatitis (4%), permanent deafness, and painful testicular swelling which can result in infertility.