Human Monkeypox: A Newly Emerged Orthopoxvirus Zoonosis in the Tropical Rain Forests of Africa

Abstract

During the course of the recently concluded smallpox eradication program, a new human orthopoxvirus infection was discovered which is caused by monkeypox virus. The disease occurs sporadically in remote villages within tropical rain forests of West and Central Africa. The disease is rare; only 155 cases having been reported from 1970 to 1983. The symptoms and signs of human monkeypox resemble those of smallpox, differing significantly only in the occurrence of lymphadenopathy with human monkeypox disease. Of 155 cases, some 80% are believed to have resulted from infection from an as yet unknown animal reservoir; the rest occurred among unvaccinated close contacts among whom a secondary attack rate of 15% was observed. Although person-to-person spread appears to have occurred in some instances, few cases were observed in the third or fourth generation of transmission and none thereafter. Since 1982, the incidence of human monkeypox infections in Zaire has increased concomitant with an intensified surveillance program. Additional reasons which might explain the increased incidence are discussed. Further surveillance and research of this primarily zoonotic infection are warranted and are in progress.

Introduction of Monkeypox into a Community and Household: Risk Factors and Zoonotic Reservoirs in the Democratic Republic of the Congo

“…[7][8][9] Although multiple animals have been shown to have neutralizing Orthopoxvirus antibodies, [9][10][11] live MPXV has only been isolated from sylvatic animals on two occasions, once from a squirrel (Funisciurus sp.) and once from a sooty mangabey (Cercocebus atys).…”

Ecology and Geography of Human Monkeypox Case Occurrences Across Africa

“…Monkeypox virus was identified as an agent of disease in 1959 when an outbreak occurred in a colony of cynomolgus monkeys (Macaca fascicularis) in Denmark (Sale et al, 2006). Human monkeypox was identified as a distinct disease in the 1970s when smallpox eradication efforts in rural areas of western and central Africa and present-day Democratic Republic of Congo (DRC) revealed a smallpox-like illness (Arita et al, 1985;Huhn et al, 2005). Since smallpox eradication, monkeypox has proven troublesome to diagnose and combat and is currently included in the select list of biologic agents considered potentially serious human health threats (CDC, 2005;USDA, 2005).…”

The Pathology of Experimental Aerosolized Monkeypox Virus Infection in Cynomolgus Monkeys (Macaca fascicularis)

“…Secondary transmission accounted for 24% of 103 cases surveyed from 1984 to 1986 (Marennikova et al, 1989). Previous estimates of the secondary attack rate for monkeypox among susceptible contacts range from as low as 3.3% to as high as 15% (Arita et al, 1985;Breman et al, 1977Breman et al, , 1980Heymann et al, 1998), compared with the 25% to 45% secondary attack rate for smallpox (Breman et al, 1977(Breman et al, , 1980. The low rate of secondary transmission may have limited the opportunity for sustained monkeypox infection among humans, and the disease occurred as self-limiting outbreaks of sporadic incidence.…”

“…Of 155 cases reported from 1970 to 1983, 80% were believed to have occurred as the result of direct transmission from an animal reservoir to the human host (Arita et al, 1985). Secondary transmission accounted for 24% of 103 cases surveyed from 1984 to 1986 (Marennikova et al, 1989).…”

“…With the eradication of smallpox and widespread discontinuation of vaccinia vaccination, monkeypox has re-emerged as a human health threat (Anonymous, 1997a(Anonymous, , 1997c(Anonymous, , 1998Arita et al, 1985;Cohen, 1997;Heymann et al, 1998;Mukinda et al, 1997). Although vaccinia vaccination protects against monkeypox, the risk of adverse effects warrants careful consideration before the vaccine is reintroduced into a population that may be immunocompromised because of a high incidence of HIV infection (Anonymous, 1997a(Anonymous, , 1997cHeymann et al, 1998;McConnell et al, 1964).…”