|The rash of monkeypox|
|Symptoms||Fever, headache, muscle pains, blistering rash, swollen lymph nodes|
|Usual onset||5-21 days post exposure|
|Duration||2 to 5 weeks|
|Diagnostic method||Testing for viral DNA|
|Differential diagnosis||Chickenpox, smallpox|
|Deaths||Up to 10%|
Monkeypox is an infectious disease caused by the monkeypox virus that can occur in certain animals including humans. Symptoms begin with fever, headache, muscle pains, swollen lymph nodes, and feeling tired. This is followed by a rash that forms blisters and crusts over. The time from exposure to onset of symptoms is around 10 days. The duration of symptoms is typically 2 to 5 weeks.
Monkeypox may be spread from handling bush meat, an animal bite or scratch, body fluids, contaminated objects, or close contact with an infected person. The virus is believed to normally circulate among certain rodents in Africa. Diagnosis can be confirmed by testing a lesion for the virus's DNA. The disease can appear similar to chickenpox.
The disease mostly occurs in Central and West Africa. It was first identified in 1958 among laboratory monkeys. The first cases in humans were found in 1970 in the Democratic Republic of the Congo. An outbreak that occurred in the United States in 2003 was traced to a pet store where imported Gambian rodents were sold.
Signs and symptoms
Limited person-to-person spread of infection has been reported in disease-endemic areas in Africa.
Monkeypox virus causes the disease in both humans and animals. It was first identified in 1958 as a pathogen of crab-eating macaque monkeys (Macaca fascicularis) being used as laboratory animals. The crab-eating macaque is often used for neurological experiments. Monkeypox virus is an Orthopoxvirus, a genus of the family Poxviridae that contains other viral species that target mammals. The virus is found mainly in tropical rainforest regions of Central and West Africa.
The virus was first discovered in monkeys (hence the name) in 1958, and in humans in 1970. Between 1970 and 1986, over 400 cases in humans were reported. Small viral outbreaks with a death rate in the range of 10% and a secondary human-to-human infection rate of about the same amount occur routinely in equatorial Central and West Africa. The primary route of infection is thought to be contact with the infected animals or their bodily fluids. The first reported outbreak outside of the African continent occurred in the United States in 2003 in the Midwestern states of Illinois, Indiana, and Wisconsin, with one occurrence in New Jersey. The outbreak was traced to a prairie dogs infected from an imported Gambian pouch rat. No deaths occurred.
Humans can be infected by an animal via a bite, or by direct contact with an infected animal’s bodily fluids. The virus can also spread from human to human, by respiratory (airborne) contact or by contact with an infected person's bodily fluids. Risk factors for transmission include sharing a bed or room, or using the same utensils as an infected patient. An increased transmission risk is associated with factors involving introduction of virus to the oral mucosa. The incubation period is 10–14 days. Prodromal symptoms include swelling of lymph nodes, muscle pain, headache, and fever prior to the emergence of the rash. The rash is usually only present on the trunk, but may spread to the palms and soles of the feet in a centrifugal distribution. The initial macular lesions exhibit a papular, then vesicular and pustular appearance.
In addition to monkeys, reservoirs for the virus are found in Gambian pouched rats (Cricetomys gambianus), dormice (Graphiurus spp.) and African squirrels (Heliosciurus, and Funisciurus). The use of these animals as food may be an important source of transmission to humans.
Diagnosis can be verified by testing for the virus. The virus does not remain very long in the blood, and hence blood testing may not detect the disease. Test results interpreted together with clinical features.
Vaccination against smallpox is assumed to provide protection against human monkeypox infection, because they are closely related viruses and the vaccine protects animals from experimental lethal monkeypox challenge. This has not been conclusively demonstrated in humans, because routine smallpox vaccination was discontinued following the apparent eradication of smallpox and owing to safety concerns with the vaccine.
Smallpox vaccine has been reported to reduce the risk of monkeypox among previously vaccinated persons in Africa. The decrease in immunity to poxviruses in exposed populations is a factor in the prevalence of monkeypox. It is attributed both to waning cross-protective immunity among those vaccinated before 1980 when mass smallpox vaccinations were discontinued, and to the gradually increasing proportion of unvaccinated individuals. 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.
The CDC does not recommend pre-exposure vaccination for unexposed veterinarians, veterinary staff, or animal control officers, unless such persons are involved in field investigations.
Currently, no treatment for monkeypox has been shown to be effective or safe. People who have been infected can be vaccinated up to 14 days after exposure.
Monkeypox as a disease in humans was first associated with an illness in the Democratic Republic of the Congo (formerly Zaire), in the town of Basankusu, Équateur Province, in 1970. A second outbreak of human illness was identified in DRC/Zaire in 1996–1997. In 2003, a small outbreak of human monkeypox in the United States occurred among owners of pet prairie dogs. The outbreak originated from Villa Park, Illinois, outside of Chicago, when an exotic animal dealer kept young prairie dogs in close proximity to an infected Gambian pouched rat (Cricetomys gambianus) recently imported from Accra, Ghana. Seventy-one people were reportedly infected, in which no fatalities occurred. In 2005, 49 cases were reported Sudan for the first time. No infected patients died. The genetic analysis suggests that the virus did not originate in Sudan but was imported, most likely from DRC.
Many more monkeypox cases have been reported in Central and West Africa, and in the Democratic Republic of Congo in particular. The collected data is often incomplete and unconfirmed which hinders realistic estimations of prevalence and incidence of monkeypox over time. Nevertheless, it was suggested that the number of reported monkeypox cases has increased and that the geographical occurrence broadened in recent years.
2003 U.S. outbreak
In May 2003, a young child became ill with fever and rash after being bitten by a prairie dog purchased at a local swap meet near Milwaukee, Wisconsin. In total, 71 cases of monkeypox were reported through June 20, 2003. All cases were traced to Gambian pouched rats imported by a Texas exotic animal distributor, from Accra, Ghana, in April, 2003. No deaths resulted. Electron microscopy and serologic studies were used to confirm that the disease was human monkeypox.
Patients typically experienced prodromal symptoms of fever, headaches, muscle aches, chills, and drenching sweats. Roughly one-third of patients had nonproductive coughs. 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, later found to be infected with the monkeypox virus.
2017–19 Nigeria outbreak
Monkeypox has been reportedly spread around southeast and south Nigeria. Some states and the federal government of Nigeria are currently seeking a way to contain it, as well as find a cure for the infected ones. It has spread to Lagos, Akwa Ibom, Bayelsa, Cross River, Delta, Ekiti, Enugu, Imo, Ibadan, Nasarawa, Niger, Rivers, and the federal capital territory. The outbreak started in September 2017 and remains ongoing across multiple states as of May 2019.
2018 United Kingdom cases
In September 2018, the United Kingdom's first case of monkeypox was recorded. The patient, a Nigerian national, is believed to have contracted monkeypox in Nigeria before travelling to the United Kingdom. According to Public Health England, the patient was staying in a naval base in Cornwall before being moved to the Royal Free Hospital's specialised infectious disease unit. People who had been in contact with the patient since he contracted the disease were contacted. A second case was confirmed in the town of Blackpool, with a further case that of a medical worker who cared for the Blackpool patient.
2019 Singapore case
On 8 May 2019, a 38-year-old man who travelled from Nigeria was hospitalised in an isolation ward at the National Centre for Infectious Diseases in Singapore, after being confirmed as the country's first case of monkeypox. As a result, 22 people have been quarantined. The case may be linked to the ongoing outbreak in Nigeria.
Monkeypox was first reported by Preben von Magnus in 1958 in laboratory Cynomolgus monkeys, when two outbreaks of a smallpox-like disease occurred in colonies of monkeys kept for research. The first report of monkeypox in humans was discovered more than a decade later, in a person with a suspected smallpox infection in the Democratic Republic of Congo during efforts to eradicate smallpox. It was subsequently reported in humans in other central and western African countries. Almost 50 cases were reported between 1970 and 1979, with more than two thirds of these being from Zaire. The other cases originated from Liberia, Nigeria, Ivory Coast and Sierra Leone.
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