Introduction
While clinically less severe than smallpox, monkeypox is a viral zoonosis (a virus that spreads from animals to people). It has symptoms that are comparable to those of smallpox. Monkeypox has replaced smallpox as the most significant orthopoxvirus for public health since smallpox was eradicated in 1980 and smallpox vaccinations were subsequently discontinued. Primarily affecting central and west Africa, monkeypox has been spreading into cities and is frequently seen close to tropical rainforests. Numerous rodent species and non-human primates serve as hosts for animals.
Key facts
• Vaccines used during the smallpox eradication programme also provided protection against monkeypox. Newer vaccines have been developed of which one has been approved for prevention of monkeypox
• Monkeypox is caused by monkeypox virus, a member of the Orthopoxvirus genus in the family Poxviridae.
• Monkeypox is usually a self-limited disease with the symptoms lasting from 2 to 4 weeks. Severe cases can occur. In recent times, the case fatality ratio has been around 3–6%.
• Monkeypox is transmitted to humans through close contact with an infected person or animal, or with material contaminated with the virus.
• Monkeypox virus is transmitted from one person to another by close contact with lesions, body fluids, respiratory droplets and contaminated materials such as bedding.
• Monkeypox is a viral zoonotic disease that occurs primarily in tropical rainforest areas of central and west Africa and is occasionally exported to other regions.
• An antiviral agent developed for the treatment of smallpox has also been licensed for the treatment of monkeypox.
• The clinical presentation of monkeypox resembles that of smallpox, a related orthopoxvirus infection which was declared eradicated worldwide in 1980. Monkeypox is less contagious than smallpox and causes less severe illness.
• Monkeypox typically presents clinically with fever, rash and swollen lymph nodes and may lead to a range of medical complications.
The pathogen
The Orthopoxvirus genus of the Poxviridae family contains the enclosed double-stranded DNA virus known as the monkeypox virus. The central African (Congo Basin) clade and the west African clade are two separate genetic clades of the monkeypox virus. In the past, the Congo Basin clade was thought to be more contagious and to produce more severe illness. The only nation where both viral clades have been discovered is Cameroon, which serves as the geographic boundary between the two groups.
Natural host of monkeypox virus
The monkeypox virus has been found to be susceptible to several animal species. This comprises non-human primates, dormice, rope and tree squirrels, Gambian pouched rats, and other species. There is still uncertainty about the monkeypox virus's natural history, and further research is required to pinpoint the precise reservoir or reservoirs and understand how the virus circulates in the wild.
Outbreaks
In the Democratic Republic of the Congo, where smallpox had been eradicated in 1968, a 9-month-old boy was the first person to be diagnosed with human monkeypox. Since then, human cases have progressively been recorded from central and west Africa, with the majority of cases coming from the rural, rain forest parts of the Congo Basin, mainly in the Democratic Republic of the Congo.
Benin, Cameroon, the Central African Republic, the Democratic Republic of the Congo, Gabon, Cote d'Ivoire, Liberia, Nigeria, the Republic of the Congo, Sierra Leone, and South Sudan are the 11 African nations where human cases of monkeypox have been documented since 1970. Unknown is the true cost of monkeypox. For instance, an epidemic with a lower case fatality ratio and a higher attack rate than typical was reported in the Democratic Republic of the Congo in 1996–1997. Monkeypox and chickenpox outbreaks that occurred simultaneously in this instance could be explained by real or apparent modifications in the dynamics of transmission produced by the varicella virus, which is not an orthopoxvirus. Nigeria has had a significant outbreak since 2017, with more than 500 suspected cases and more than 200 confirmed cases.
Given that it affects the rest of the world in addition to countries in west and central Africa, monkeypox is a disease of worldwide public health significance. The first monkeypox outbreak outside of Africa occurred in the United States of America in 2003, and contact with pet prairie dogs that had the disease was to blame. These pets had been kept with dormice and pouched rats from Ghana that were imported from the Gambia. Over 70 cases of monkeypox were brought on by this outbreak in the US. Travelers from Nigeria to Israel in September 2018, the United Kingdom in September 2018, December 2019, May 2021, and May 2022, Singapore in May 2019, and the United States of America in May 2019 have also been reported to have monkeypox.
Transmission
Direct contact with the blood, body fluids, cutaneous or mucosal lesions of infected animals can result in animal-to-human (zoonotic) transfer. Numerous animals in Africa, including rope squirrels, tree squirrels, Gambian pouched rats, dormice, various species of monkeys, and others, have shown signs of monkeypox virus infection. Rodents are the most plausible candidates for the monkeypox natural reservoir, though this has not yet been determined. Eating undercooked meat and other diseased animal products is a potential risk factor. People who live in or close to forests may be indirectly or minimally exposed to diseased animals.
Close contact with respiratory secretions, skin sores on an infected person, or recently contaminated objects can cause human-to-human transmission. Health professionals, family members, and other close contacts of current patients are more at risk because droplet respiratory particles typically require extended face-to-face contact. The number of person-to-person infections in a community's longest documented chain of transmission has increased from 6 to 9 in recent years. This might be an indication of a general decline in immunity brought on by the end of smallpox vaccination campaigns. Congenital monkeypox can result through transmission through the placenta, which can also happen during intimate contact during labor and after delivery. Despite the fact that intimate physical contact is an established risk factor for transmission, it is yet unknown if
Signs and symptoms
The incubation period (interval from infection to onset of symptoms) of monkeypox is usually from 6 to 13 days but can range from 5 to 21 days.
The infection can be divided into two periods:
• the invasion period (lasts between 0–5 days) characterized by fever, intense headache, lymphadenopathy (swelling of the lymph nodes), back pain, myalgia (muscle aches) and intense asthenia (lack of energy). Lymphadenopathy is a distinctive feature of monkeypox compared to other diseases that may initially appear similar (chickenpox, measles, smallpox)
• the skin eruption usually begins within 1–3 days of appearance of fever. The rash tends to be more concentrated on the face and extremities rather than on the trunk. It affects the face (in 95% of cases), and palms of the hands and soles of the feet (in 75% of cases). Also affected are oral mucous membranes (in 70% of cases), genitalia (30%), and conjunctivae (20%), as well as the cornea. The rash evolves sequentially from macules (lesions with a flat base) to papules (slightly raised firm lesions), vesicles (lesions filled with clear fluid), pustules (lesions filled with yellowish fluid), and crusts which dry up and fall off. The number of lesions varies from a few to several thousand. In severe cases, lesions can coalesce until large sections of skin slough off.
Monkeypox is usually a self-limited disease with the symptoms lasting from 2 to 4 weeks. Severe cases occur more commonly among children and are related to the extent of virus exposure, patient health status and nature of complications. Underlying immune deficiencies may lead to worse outcomes. Although vaccination against smallpox was protective in the past, today persons younger than 40 to 50 years of age (depending on the country) may be more susceptible to monkeypox due to cessation of smallpox vaccination campaigns globally after eradication of the disease. Complications of monkeypox can include secondary infections, bronchopneumonia, sepsis, encephalitis, and infection of the cornea with ensuing loss of vision. The extent to which asymptomatic infection may occur is unknown.
The case fatality ratio of monkeypox has historically ranged from 0 to 11 % in the general population and has been higher among young children. In recent times, the case fatality ratio has been around 3–6%.
Article Source: https://www.who.int/news-room/fact-sheets/detail/monkeypox