also known as Arestyvir, has been licensed for use in humans infected with orthopoxviruses, but its specific efficacy against monkeypox in people has not yet been evaluated. Other possible agents, including a derivative of cidofovir (CMX001/ Brincidofovir) are in clinical trials. Vaccinia immune globulin, which was used at one time to treat smallpox, might also be tried, especially in those who are immunocompromised. Prevention Smallpox (vaccinia) vaccination appears to provide some protection from monkeypox, and it has been recommended for some healthy people in occupations at high risk of exposure. Post–exposure vaccination also seems to be helpful, and may be offered to people who are exposed to a monkeypox-infected person or animal. This vaccine cannot be used in those who are immunocompromised. The general population is not currently vaccinated in endemic areas of Africa, due to the expense of the vaccine and the risk of serious side effects, particularly in areas where undiagnosed severe T cell immunodeficiencies (e.g., untreated HIV-1 infection) may be relatively common. A vaccine specifically for monkeypox is in clinical trials in Africa, as of 2020. As a routine preventive measure, care should be taken to treat and cover breaks in the skin when working with nonhuman primates or other animals that may be hosts for monkeypox virus. Infection control procedures such as good hygiene, frequent hand washing, disinfection of surfaces and equipment, and the use of personal protective equipment (PPE) are important during contact with animals suspected to have monkeypox. Necropsies should be done in Biosafety Level 2 laboratories, using a certified Class II Biological Safety Cabinet. Anyone who has been in contact with a monkeypox suspect should contact a health care provider immediately. Health authorities (e.g., the local or state health department) must also be informed. Isolation of infected patients and good infection control measures are helpful in preventing person-to-person transmission. Ring vaccination might also be used in some outbreaks. Because the full host range of monkeypox virus is uncertain, infected individuals should also limit their contact with any pet, particularly species known to be susceptible to this virus. Morbidity and Mortality In Africa, monkeypox is usually seen in rural populations, and is most common in children and young adults. Most cases occur among people who live in or near heavily forested areas, where the virus is thought to be endemic in animals, though outbreaks have been reported elsewhere. Clinical cases often occur after contact with wild small mammals, which are caught for food and other purposes, but person-to-person transmission and family clusters appear to be significant in some outbreaks. In the past, monkeypox was thought to be a rare disease; however, outbreaks and sporadic cases have increasingly been reported from Africa during the last few decades. Waning immunity from smallpox vaccinations may be a factor, as the disease predominantly affects young people born after vaccination campaigns ended. Other societal factors (e.g., changes resulting from poverty or war) that increase exposure to the reservoir hosts are also plausible, as are some impacts from increased awareness and reporting. Most outbreaks have occurred in central Africa and are caused by the Congo Basin clade, which is more virulent. Until recently, clinical cases caused by the West African clade were seen only rarely. The first significant outbreak in recent years occurred in 2003 in the U.S. and was linked to imported exotic pets, which disseminated the virus to pet prairie dogs and hence to humans. Seventy-two human infections were reported, including 37 that were laboratory confirmed. Most cases occurred after direct contact with pet prairie dogs. African rodents appeared less likely to transmit the disease to humans, possibly due to different types of behavioral interactions with these animals. In 2017-2018, a West African virus caused at least 132 confirmed and approximately 300 suspected cases in Nigeria. This event, the first significant outbreak in Nigeria since the 1970s, occurred after floods that may have increased human exposure to rodents. Many cases appeared to result from person-to-person propagation of the virus. Since then, increased surveillance has uncovered sporadic, ongoing human cases in Nigeria. Serological surveillance has also Monkeypox © 2004-2022 www.cfsph.iastate.edu page 6 of 9 revealed antibodies to orthopoxviruses in some healthy young people in West Africa who report no previous illness suggestive of monkeypox. The highest risk of death from monkeypox is in infants, young children and immunocompromised individuals. Reported case fatality rates in outbreaks caused by Congo Basin (Central African) strains reach 10% or more, and are occasionally as high as 20-25% in some smaller clusters. However, there is still uncertainty in these estimates, as milder cases might be missed and co-morbidities are common in affected areas. Clinical cases caused by West African clade viruses seem to be milder. No deaths occurred during the outbreaks in the U.S., while 7 deaths were seen in the recent outbreak in Nigeria. Four of these fatalities occurred in immunocompromised individuals, two of whom had