The monkeypox virus, belonging to the orthopoxvirus group of viruses, causes monkeypox, which is related to variola and cowpox. People can contract monkeypox from an infected animal through a bite or by direct contact with the animal’s blood, body fluids, or lesions. It may also be acquired by ingestion of the infected animal’s inadequately cooked flesh. The infection is spread person to person via respiratory droplets during direct and prolonged face-to-face contact. Monkeypox is less infectious than smallpox, but it can also be spread through direct contact with an infected person’s body fluids or with virus-contaminated objects, such as bedding or clothing.

Complications of monkeypox reported from African outbreaks include pitted scars, deforming scars, secondary bacterial infection, bronchopneumonia, respiratory distress, keratitis, corneal ulceration, blindness, septicemia, and encephalitis. Death may also occur.

The signs and symptoms of monkeypox are similar to those of smallpox but milder. After an incubation period of about 12 days, the patient may report fever, headache, sore throat, cough, muscle aches, backache, swollen lymph nodes, and a general feeling of discomfort and exhaustion. Monkeypox, smallpox, and chickenpox are very similar, and the most reliable clinical sign that differentiates monkeypox from smallpox or chickenpox is the enlarged lymph nodes seen in monkeypox, especially the submental, submandibular, cervical, and inguinal nodes. A papular rash begins on the face or any other area of the body (even in areas that are usually covered) within 1 to 3 days after the onset of fever. The lesions go through several stages before crusting and falling off. Enanthema, which are lesions and inflammation of the pharyngeal, conjunctival, and genital mucosae, may develop. Exanthema lesions appearing in crops may occur within a particular body region and evolve synchronously over 14 to 21 days. The lesions do not have a strong centrifugal distribution and progress from macules to papules to vesicles and pustules. Umbilication, crusting, and desquamation follow. Most lesions are 0.2 to 0.6″ (3 to 15 mm) in diameter and appear often on the face, trunk, extremities, and scalp. Lesions may also be seen on the palms of the hands and soles of the feet. Necrosis, petechiae, and ulceration may occur. Pruritus may be present, but pain may indicate a secondary bacterial infection. In children, the lesions may appear as erythematous papules that are 1 to 5 mm in diameter, suggestive of mosquito bite reactions. Subtle umbilication may be seen. The patient may develop deep pock scars as the lesions resolve. The duration of illness is 2 to 4 weeks.