Transmission can be via direct contact, aerosol, ingestion, or parenteral administration. Person to person transmission can occur. Usually exhibit a high morbidity and low mortality. Clinical signs may be inapparent or an animal may exhibit fever, lymphadenopathy, and cutaneous eruptions of the extremities, trunk, lips, or face. Cynomologus monkeys seem to be most severely affected.
Death is uncommon except in infant monkeys.
Severe complications include bronchopneumonia, vomiting, and diarrhea. Although the disease is not common in man it is important from the standpoint of differentiating it from smallpox. On histological examination epidermal cells contain eosinophilic cytoplasmic and intranuclear inclusions. Vaccination with vaccinia virus is protective in both man and nonhuman primates.