Monkeypox is an exotic infectious disease caused by the monkeypox virus. The disease was first identified in laboratory monkeys, thus providing it with its name, but in its natural state it seems to infect rodents more than primates. The disease is most prevalent in Central and West Africa, but an outbreak occurred also in the United States in 2003.[1]
Human monkeypox is a zoonotic viral disease that occurs primarily in remote villages of Central and West Africa in proximity to tropical rainforests where there is more frequent contact with infected animals. Monkeypox is usually transmitted to humans from rodents, pets, and primates through contact with the animal's blood or through a bite. Human monkeypox can be difficult to distinguish clinically from smallpox (to which it is closely related) and chickenpox (to which it is not).[2]
Epidemiology
In addition to monkeys, giant pouched rats (Cricetomys sp.), dormice (Graphiurus sp.) and African squirrels (Heliosciurus, Funisciurus) have all been implicated as reservoirs of the virus. The use of these animals as food may be an important source of transmission to humans.[citation needed]
Monkeypox as a disease was first associated with human illness in Zaire and West Africa during 1970–1971. A second outbreak of human illness was identified in Zaire in 1996–1997. In 2003, a small outbreak of human monkeypox in the United States occurred among owners of pet prairie dogs.[3] The prairie dogs had been exposed to an infected Gambian pouched rat (Cricetomys gambianus).
A second African focus of infection has been discovered in Sudan. No infected patients died.[4]
Monkeypox disease in animals
The symptoms of a sick animal include: listlessness, ocular and nasal discharges, coughing, hair loss sometimes accompanied by painful scabs, and pneumonia. Look for nodules similar to mosquito bites and inflammation of the lymph glands.
Monkeypox disease in humans
Symptoms and course
In humans, monkeypox is similar to smallpox, although it is often milder. Unlike smallpox, monkeypox causes lymph nodes to swell (lymphadenopathy). The incubation period for monkeypox is about 12 days (range 7 to 17 days). The illness begins with fever, headache, muscle aches, backache, swollen lymph nodes, a general feeling of discomfort, and exhaustion. Within 1 to 3 days (sometimes longer) after the appearance of fever, the patient develops a papular rash i.e., raised bumps, often first on the face but sometimes initially on other parts of the body. The lesions usually develop through several stages before crusting and falling off.
It is assumed that vaccination against smallpox would provide protection against human monkeypox infection considering that they are closely related viruses and the vaccine protects animals from experimental lethal monkeypox challenge.[5] This has not been conclusively demonstrated in humans because routine smallpox vaccination was discontinued following the apparent eradication of smallpox and due to safety concerns with the vaccine. Limited person-to-person spread of infection has been reported in disease-endemic areas in Africa. Case-fatality ratios in Africa have ranged from 1% to 10%.[6]
Prevention and treatment
Currently, there is no proven, safe treatment for monkeypox. Smallpox vaccine has been reported to reduce the risk of monkeypox among previously vaccinated persons in Africa. The United States Centers for Disease Control and Prevention (CDC) recommends that persons investigating monkeypox outbreaks and involved in caring for infected individuals or animals should receive a smallpox vaccination to protect against monkeypox. Persons who have had close or intimate contact with individuals or animals confirmed to have monkeypox should also be vaccinated. These persons can be vaccinated up to 14 days after exposure. CDC does not recommend preexposure vaccination for unexposed veterinarians, veterinary staff, or animal control officers, unless such persons are involved in field investigations.
2003 U.S. outbreak
Through June 18, 2003, there were 93 cases of monkeypox in the United States including Wisconsin (44 cases), Indiana (24), Illinois (19), Ohio (4), Kansas (1), Missouri (1), and New Jersey (1). Analysis of the first 53 cases showed all 50[clarification needed] had contact with prairie dogs that were purchased from Phil's Pocket Pets of Villa Park, Illinois.[7] Electron microscopy and serologic studies were used to confirm that the disease was human monkeypox.
The onset of the illness among the patients in the United States began in early May 2003. Patients typically experienced a prodrome consisting of fever, headaches, myalgias, chills, and drenching sweats. Roughly one-third of patients had nonproductive cough. This prodromal phase was followed 1–10 days later by the development of a papular rash that typically progressed through stages of vesiculation, pustulation, umbilication, and crusting. In some patients, early lesions had become ulcerated. Rash distribution and lesions occurred on head, trunk, and extremities; many of the patients had initial and satellite lesions on palms, soles, and extremities. Rashes were generalized in some patients. After onset of the rash, patients generally manifested rash lesions in different stages. All patients reported direct or close contact with prairie dogs, most of which were sick. Illness in prairie dogs was frequently reported as beginning with a blepharoconjunctivitis, progressing to presence of nodular lesions in some cases. Some prairie dogs died from the illness, while others reportedly recovered.
References
- ^ Bayer-Garner IB (2005). "Monkeypox virus: histologic, immunohistochemical and electron-microscopic findings". J. Cutan. Pathol. 32 (1): 28–34. doi:10.1111/j.0303-6987.2005.00254.x. PMID 15660652.
- ^ Jezek Z, Szczeniowski M, Paluku KM, Mutombo M, Grab B (1988). "Human monkeypox: confusion with chickenpox". Acta Trop. 45 (4): 297–307. PMID 2907258.
- ^ "What You Should Know About Monkeypox" (PDF). Fact Sheet. Centers for disease control and prevention. 2003-06-12. http://www.cdc.gov/ncidod/monkeypox/pdf/factsheet2.pdf. Retrieved 2008-03-21.
- ^ Damon IK, Roth CE, Chowdhary V (2006). "Discovery of monkeypox in Sudan". N. Engl. J. Med. 355 (9): 962–3. doi:10.1056/NEJMc060792. PMID 16943415. http://content.nejm.org/cgi/content/full/355/9/962.
- ^ Marriott KA, Parkinson CV, Morefield SI, Davenport R, Nichols R, Monath TP (2008). "Clonal vaccinia virus grown in cell culture fully protects monkeys from lethal monkeypox challenge". Vaccine 26 (4): 581–8. doi:10.1016/j.vaccine.2007.10.063. PMID 18077063. http://linkinghub.elsevier.com/retrieve/pii/S0264-410X(07)01257-1.
- ^ Hutin YJ, Williams RJ, Malfait P, et al. (2001). "Outbreak of human monkeypox, Democratic Republic of Congo, 1996 to 1997". Emerging Infect. Dis. 7 (3): 434–8. PMID 11384521. http://www.cdc.gov/ncidod/eid/vol7no3/hutin.htm.
- ^ Medscape Monkeypox Review[1]
External links
Note: much of the original text of this article is taken from public domain CDC (Center for Disease Control) and NIH (National Institute of Health) sources.
