Monkeypox, now often referred to as mpox, is a viral disease that has garnered global attention due to recent outbreaks outside its historically recognized regions. It represents a zoonotic infection, meaning it can transmit between animals and humans. The disease is caused by the monkeypox virus, which is closely related to the smallpox virus.
Understanding Monkeypox as a Disease
Mpox is caused by the monkeypox virus (MPXV), a double-stranded DNA virus belonging to the Orthopoxvirus genus within the Poxviridae family. This genus also includes the variola virus, responsible for smallpox, as well as cowpox and vaccinia viruses. The monkeypox virus has two main genetic groups, known as clades: Clade I, historically associated with Central Africa, and Clade II, linked to West Africa. Clade I causes more severe disease and has a higher mortality rate compared to Clade II. While sharing similarities with smallpox, mpox presents with milder symptoms and a lower fatality rate.
Historical Presence and Endemic Regions
The monkeypox virus was first identified in 1958 during outbreaks of a pox-like disease in research monkey colonies in Copenhagen, Denmark. The first documented human case of mpox occurred in 1970, involving a nine-month-old boy in the Democratic Republic of the Congo (DRC), discovered during smallpox eradication efforts in Africa.
Following this initial human case, mpox has been sporadically reported in the tropical rainforest regions of Central and West Africa. Countries in Central and West Africa, including the Democratic Republic of the Congo (DRC), have historically reported cases, with the DRC consistently reporting the majority.
While named “monkeypox,” the natural animal reservoir for the virus is not monkeys, but is various small mammals, particularly rodents found in tropical African forests. African rope squirrels and giant pouched rats have been identified as likely hosts. Transmission to humans occurs through contact with infected animals, such as through bites, scratches, or handling infected meat.
Transmission and Clinical Presentation
Mpox can spread through various routes, including direct contact with an infected person’s lesions, body fluids, or scabs. It can also be transmitted through prolonged face-to-face contact via large respiratory droplets, or by touching contaminated materials like clothing or bedding. Animal-to-human transmission can occur from bites or scratches from infected animals, or during activities like hunting or preparing infected meat.
After exposure to the monkeypox virus, the incubation period ranges from 3 to 17 days, during which the individual is not contagious. The illness begins with flu-like symptoms, including fever, headache, muscle aches, backache, chills, and exhaustion. A distinguishing symptom of mpox is the swelling of lymph nodes, which helps differentiate it from other diseases like chickenpox or smallpox.
Within one to three days after the onset of fever, a characteristic rash appears. This rash can develop on the face, inside the mouth, and on the hands, feet, chest, genitals, or anus. The rash progresses through several stages: flat, red spots (macules) turn into raised bumps (papules), then fluid-filled blisters (vesicles), followed by pus-filled lesions (pustules), and finally crusts or scabs that fall off. The lesions remain contagious until all scabs have fallen off and a new layer of skin has formed underneath, with the entire illness lasting two to four weeks.
Prevention, Treatment, and Public Health Response
Prevention of mpox involves several strategies, including vaccination and avoiding contact with infected animals. Vaccines originally developed for smallpox, such as JYNNEOS and ACAM2000, are effective against mpox. JYNNEOS is a non-replicating vaccine approved for individuals at high risk of infection, administered as a two-dose series. These vaccines can be given both before exposure (pre-exposure prophylaxis) and within a few days after exposure (post-exposure prophylaxis) to help prevent illness or reduce its severity.
Most mpox cases are self-limiting, meaning individuals recover within a few weeks without specific treatment. Supportive care, such as managing pain and fever, ensuring adequate hydration and nutrition, and preventing secondary infections, is important. For severe cases, or in individuals who are immunocompromised, specific antiviral medications may be considered.
Tecovirimat (TPOXX) is an antiviral drug approved for smallpox, which also shows activity against monkeypox. It can be administered orally or intravenously. Other antivirals, like cidofovir and brincidofovir, have also shown activity against poxviruses and may be used, although tecovirimat is preferred due to its safety profile. Public health responses in endemic regions and during outbreaks focus on surveillance, contact tracing, isolating infected individuals, and educating communities about transmission and prevention.