genitalia, and transplacental transmission has been documented. In Africa, clinical cases have often been linked to handling, preparing and eating wild animals, but person-to-person transmission was also significant in some outbreaks. In the U.S., most cases occurred among people who had close direct contact with prairie dogs; some infections were apparently acquired in scratches and bites, or through open wounds. Monkeypox virus has been isolated from humans for up to 18 days after the onset of the rash, and scabs shed during recovery were found to contain significant amounts of infectious virus. Person-toperson transmission does not seem to be capable of maintaining the virus in human populations. Disinfection Disinfectants reported to be effective for orthopoxviruses include sodium hypochlorite, chloroxylenol-based household disinfectants, glutaraldehyde, formaldehyde and paraformaldehyde. During an outbreak in the U.S., the U.S. Centers for Disease Control and Prevention (CDC) recommended 0.5% sodium hypochlorite or other EPA–approved high–level disinfectants. Incineration or autoclaving is appropriate for some contaminated materials. Infections in Animals Incubation Period Reported incubation periods in experimentally infected animals range from 3 days to about 2 weeks in most cases. The incubation period was slightly longer (11 to 18 days) in prairie dogs infected by exposure to fomites than after direct exposure. Clinical Signs Nonhuman primates The predominant syndrome in nonhuman primates is a self–limited rash, which begins as small cutaneous papules that develop into pustules, then crust over, and may leave small scars when the crusts drop off. A typical monkeypox lesion has a red, necrotic, depressed center, surrounded by epidermal hyperplasia. The number of lesions varies from a few individual pocks to extensive, coalescing lesions. They sometimes affect the entire body, but may be more common on the face, limbs, palms, soles and tail. Some animals have only skin lesions, which may be accompanied by a fever or lymphadenopathy, but do not appear to be otherwise ill. In more severe cases, there may also be respiratory signs (coughing, nasal discharge, dyspnea), ocular discharge, anorexia, facial edema or oral ulcers. Respiratory signs of varying severity, with minimal skin lesions (e.g., a single lesion on the lip), were observed in some wild chimpanzees during an outbreak caused by a West African virus. Other animals in this outbreak had more classical signs including a rash. Most naturally infected animals recover; however, fatalities are sometimes seen, particularly in infant monkeys. Asymptomatic infections are also possible. Prairie dogs and other rodents In prairie dogs, the clinical signs may include fever, depression, anorexia, blepharoconjunctivitis (often the initial sign), respiratory signs (nasal discharge, sneezing and/or coughing, respiratory distress), diarrhea, skin lesions similar to those in nonhuman primates, and oral ulcers. Lymphadenopathy was seen in naturally infected prairie Monkeypox © 2004-2022 www.cfsph.iastate.edu page 3 of 9 dogs, but did not occur in all experimentally infected animals. Elevated serum levels of liver enzymes have also been reported. Some cases are fatal, and experimentally infected prairie dogs sometimes died without developing lesions on the skin or mucous membranes. Similar clinical signs have been reported in other naturally or experimentally infected rodents; however, not all animals developed skin lesions. Intranasally inoculated dormice, which often died, had only nonspecific signs such as lethargy, an unkempt hair coat, a hunched posture, conjunctivitis and dehydration. Some naturally infected Gambian giant pouched rats had asymptomatic infections or mild illnesses, with no respiratory signs and limited skin lesions, but other animals died, and experimentally infected pouched rats sometimes became moderately to severely ill, with skin and oral lesions, ocular lesions and nonspecific signs of illness. Pox lesions were found in a wild Thomas’s rope squirrel (Funisciurus anerythrus) in Africa that was found infected with a Congo Basin strain. Some rope squirrels (Funisciurus anerythrus) inoculated with a Congo Basin strain developed skin and oral lesions, respiratory signs and, in one case, corneal lesions. However, African squirrels administered a high viral dose in an earlier study died with a generalized, nonspecific illness, and skin lesions occurred only in a few animals that received a lower, nonfatal dose. Post Mortem Lesions Click to view images At necropsy, the skin may contain one or more papules, umbilicated pustules (“pocks”) with central necrosis, or crusts over healing lesions. Ulcers, erosions or lesions with necrotic centers may be found in the mouth of some animals. Peripheral lymphadenopathy is common but not always present. Conjunctivitis or blepharoconjunctivitis may also be noted. Pox lesions (white plaques or small, white, firm, deeply embedded foci with umbilicated necrotic centers) are sometimes detected on internal organs or in the stomach and small intestine. Some animals may have other internal lesions including lung involvement (e.g., pleuritis, consolidation of the lung, pulmonary edema, multifocal necrotizing pneumonitis or bronchoalveolar pneumonia),