Monkeypox

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.[2]

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.[11] The primary route of infection is thought to be contact with the infected animals or their bodily fluids.[11] 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 dog infected from an imported Gambian pouch rat.[3] 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 person. An increased transmission risk is associated with factors involving introduction of virus to the oral mucosa.[12] 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.[12]

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.

Gambian pouched rat

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.[19] 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.[20] Electron microscopy and serologic studies were used to confirm that the disease was human monkeypox.

People with monkeypox typically experienced prodromal symptoms of fever, headaches, muscle aches, chills, and drenching sweats. Roughly one-third of infected people 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 people, early lesions had become ulcerated. Rash distribution and lesions occurred on head, trunk, and extremities; many of the people had initial and satellite lesions on palms, soles, and extremities. Rashes were generalized in some people. After onset of the rash, people generally manifested rash lesions in different stages. Everyone affected reported direct or close contact with prairie dogs, later found to be infected with the monkeypox virus.[21]

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.[22]

In September 2018, the United Kingdom's first case of monkeypox was recorded. The person, a Nigerian national, is believed to have contracted monkeypox in Nigeria before travelling to the United Kingdom.[23] According to Public Health England, the person 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 person since he contracted the disease were contacted.[24] A second case was confirmed in the town of Blackpool,[25][26] with a further case that of a medical worker who cared for the case from Blackpool.[27] A fourth case occurred on 3 December 2019, when monkeypox was diagnosed in a person in south west England. They were travelling to the UK from Nigeria.[28]

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 were quarantined.[29] The case may be linked to the ongoing outbreak in Nigeria.[22]