Monkeypox

Monkey disease (Monkeypox) is a zoonotic disease caused by the Monkeypox virus (MPXV), classified within the Orthopoxvirus genus of the Poxviridae family. Its clinical symptoms resemble those of smallpox; however, its transmissibility and mortality rate are lower compared to smallpox. MPXV is an enveloped virus with a double-stranded DNA genome and is genetically related to the Variola, Vaccinia and Cowpox viruses through close relationships.

History of the Disease

Disease was first identified in 1958 in Denmark among laboratory monkeys. However, subsequent research revealed that the natural host of the virus is likely not monkeys but certain rodent species. The first confirmed human case was detected in 1970 in the Democratic Republic of the Congo in a nine-month-old boy. This case emerged during the smallpox eradication campaign, after which monkeypox became endemic particularly in Middle and West African regions.

Over time, increased international travel and the exotic animal trade have contributed to the spread of the disease to non-endemic areas. Indeed, in 2003, more than 70 cases reported in United States of America were linked to rodents imported from Ghana. This situation is significant as it demonstrated the global transmission potential of the disease.

In monkeypox, which typically follows a self-limiting clinical course, symptoms usually resolve within 2 to 4 week. Nevertheless, more severe clinical presentations and complications can occur in individuals with compromised immune systems, children, and pregnant women. Due to these characteristics, the disease is not only an individual health concern but also holds importance from a people health perspective.

It is known that vaccines developed against smallpox provide approximately 85% protection against MPXV. However, following the eradication of smallpox in 1980, vaccination programs were discontinued, leading to a decline in population-level immunity against Orthopoxviruses in subsequent generations.

An image generated by artificial intelligence illustrating monkeypox disease.

Natural Hosts and Reservoirs

The natural reservoir of the monkeypox virus has not been definitively identified, but epidemiological and laboratory studies have shown that many animal species are susceptible to this virus. Major suspected hosts include tree squirrels, gambian pouched rats, fat-tailed mice, and other small rodent species place. Humans and monkeys are accidental hosts in this context, and it is believed that the virus primarily circulates in nature through rodents.

Infections in animals are often asymptomatic, allowing infected animals difference to spread the virus into the environment without detection. This complicates efforts to prevent zoonotic transmission and hinders virus control. Therefore, wildlife monitoring programs, identification of reservoir species, and analysis of human-animal interface interactions are of critical importance for developing effective prevention strategies.

Epidemiology and Outbreaks

The first reported human case of monkeypox occurred in 1970 in the Democratic Republic of the Congo. In the following years, sporadic small outbreaks occurred in Central and Western Africa. Outbreaks were reported in the Congo in 1996–1997 and in Nigeria in 2017.

During the Nigeria outbreak, over 500 suspected and more than 200 confirmed cases were identified, with a reported mortality rate of approximately 3%.

In 2003, an outbreak in the United States linked to animals imported from Ghana was recorded as the first major monkeypox outbreak outside Africa. This outbreak resulted in over 70 infections and demonstrated that zoonotic transmission could occur on a global scale.

By 2022, there was a marked increase in case numbers, prompting the World Health Organization (WHO) to declare the disease a “Public Health Emergency of International Concern” (PHEIC) on 21 June 2022. During this period, consecutive cases were reported in non-endemic countries, establishing monkeypox as a global public health priority.

Transmission Routes

The Monkeypox virus can transmit from infected animals to humans (zoonotic transmission) and from infected individuals to other individuals (human-to-human transmission).

Animal-to-human transmission typically occurs through contact with the blood, bodily fluids, skin lesions, or raw or undercooked meat of infected animals. Bites or scratches from infected animals can also contribute to transmission.

Human-to-human transmission primarily occurs through direct contact with skin lesions of infected individuals, indirect contact with contaminated objects (towel, veil, clothing, etc.), or prolonged close respiratory contact (via droplets). Additionally, transmission from mother to fetus via the placenta (congenital transmission) is possible.

Considering all these transmission routes, both individual hygiene measures and society-based isolation strategies are of critical importance for preventing disease spread.

An image generated by artificial intelligence illustrating monkeypox disease.

Clinical Signs and Course

The incubation period of monkeypox typically ranges from 6 to 13 days; however, in some cases it may extend from 5 to 21 days. Infection usually begins with a prodromal phase characterized by systemic symptoms such as fever, headache, lymphadenopathy, myalgia, back pain, and fatigue. These symptoms are typically followed by a skin rash.

• Rashes usually begin on the face and spread to other parts of the body. They progress through five stages: macule → papule → vesicle → pustule → crust.
• Lesions typically evolve synchronously. Rashes may appear on the face, palms, soles, inside the mouth, and sometimes the genital area.
• The overall course of the disease is usually mild, but complications can occur in some patients. Particularly in immunocompromised individuals, children, and pregnant women, more severe clinical presentations and complications such as encephalitis, bronchopneumonia, and secondary bacterial infections have been reported.

Diagnosis and Laboratory Methods

A definitive diagnosis of monkeypox is based on the molecular detection of the virus’s genetic material. Real-Time PCR (RT-PCR) is the most sensitive and specific diagnostic method, particularly when applied to samples taken from skin lesions. Serological tests and viral culture or microscopic examination serve as supportive diagnostic tools.

Differential diagnosis must consider diseases such as chickenpox (varicella), smallpox (variola), herpes simplex infections, syphilis, bacterial skin infections, and certain drug reactions.

Proper sampling, appropriate transport conditions, and collaboration with reference laboratories are essential for accurate diagnosis.

Warning: The content in this article is provided solely for general encyclopedic information purposes. The information presented here should not be used for diagnosis, treatment, or medical guidance. Always consult a physician or qualified healthcare professional before making any health-related decisions. The author and SPHERE Encyclopedia assume no responsibility for any consequences arising from the use of this information for diagnostic or therapeutic purposes.