Monkeypox virus is a double-stranded DNA virus in the orthopoxvirus genus, related to variola and vaccinia, that historically caused zoonotic outbreaks primarily in Central and West Africa. The term monkeypox refers to a disease first identified in laboratory monkeys in 1958, though small mammals such as rodents and squirrels are now considered the main natural reservoir. Human cases typically begin with fever, rash, and swollen lymph nodes, evolving through macular, papular, vesicular, and pustular stages over two to four weeks. Transmission occurs through close contact with lesions, bodily fluids, contaminated materials, and respiratory droplets during prolonged face-to-face exposure, with person-to-person spread more common in the current global context than in earlier sporadic outbreaks.
Origin and discovery of monkeypox
Monkeypox virus was first isolated in 1958 following outbreaks of pox-like disease in colonies of laboratory monkeys kept for research, which gave the disease its name. The virus was later detected in a range of African rodents and nonhuman primates, establishing zoonotic cycles in parts of sub-Saharan Africa. Genetic studies indicate two distinct clades: the Congo Basin (Central African) clade and the West African clade, with differing levels of virulence. Historical sporadic human cases were often linked to direct contact with infected animals through hunting, trapping, or habitat encroachment, before the recognition of larger human-to-human transmission events in multiple countries in 2022.
Signs and symptoms of infection
Incubation and initial features
The incubation period for monkeypox is typically six to 13 days but can range from five to 21 days. Early symptoms are nonspecific and may include fever, headache, fatigue, muscle aches, and swollen lymph nodes, sometimes accompanied by chills or respiratory signs. Within one to three days, a rash appears and progresses through distinct stages: macules, papules, vesicles, pustules, and finally crusts, which fall off. The rash often begins on the face and may spread to the palms, soles, mouth, throat, genital area, and anus. Lesions can be painful or itchy, and the illness usually resolves in two to four weeks without treatment in milder cases.
Modes of transmission
Transmission of monkeypox virus occurs primarily through direct contact with infectious lesions, scabs, or body fluids. This can happen during skin-to-skin contact, including sexual contact, touching contaminated fabrics or surfaces such as bedding and clothing, and exposure to respiratory secretaries during prolonged close interactions. Entry routes include broken skin, the respiratory tract, and mucous membranes of the eyes, nose, or mouth. While short-range droplet transmission may play a role in household or healthcare settings, prolonged face-to-face contact is typically required for spread. Vertical transmission from pregnant person to fetus and possible transmission via infected animal bites or scratches are documented routes in endemic regions.
Diagnosis and testing considerations
Diagnosis begins with clinical evaluation and a careful exposure history, considering travel, contact with rash or ill persons, and occupational risk. Health care providers collect samples from multiple vesicular or pustular lesions for polymerase chain reaction (PCR) testing, which is the preferred method to confirm orthopoxvirus infection and, through further analysis, to differentiate monkeypox from other poxviruses. Orthopoxvirus antigen detection tests or serology may support the diagnosis in certain contexts, but PCR remains the standard for acute cases. Public health laboratories often perform confirmatory testing to ensure accurate identification and characterization of the virus genotype.
Treatment and management approaches
Supportive care forms the mainstay of management for most individuals with monkeypox, focusing on fever control, pain relief, skin care, and prevention of secondary infection. Oral or intravenous fluids may be necessary for dehydration, and analgesics can help manage discomfort. In higher-risk cases, such as severe disease, immunocompromised patients, or complications, clinicians may consider antiviral treatment; tecovirimat is an option authorized for orthopoxvirus infections under certain protocols. Smallpox vaccines, including ACAM2000 and newer MVA-based vaccines, can provide protection when administered before or shortly after exposure, and vaccinia immune globulin may be considered in selected situations. Decisions about specific treatments are guided by clinical severity, local guidelines, and expert consultation.
Prevention and public health measures
Vaccination and behavioral strategies
Preventing monkeypox centers on minimizing exposure and reducing transmission opportunities. Key strategies include avoiding close contact with people who have a visible rash, limiting skin-to-skin interactions during illness, not sharing utensils, cups, or bedding, and practicing thorough hand hygiene with soap and water or alcohol-based hand rub. Health care and public health workers use appropriate personal protective equipment, including gloves and respiratory protection when indicated, especially during aerosol-generating procedures. Vaccination is recommended for specific groups, such as those with known or suspected exposure and higher-risk individuals in outbreak settings. Public communication, case investigation, and contact tracing remain central to controlling ongoing transmission and protecting vulnerable populations.
Notable case patterns and timelines
Before 2022, monkeypox cases were rare and primarily reported in endemic countries following travel or through imported animals. The 2022 outbreak marked the first large-scale, multi-country spread with substantial human-to-human transmission, including within communities not previously considered high risk. The index cases in many settings were identified among men who have sex with men, though transmission has since been documented across diverse networks. Overall severity has been lower than historic smallpox, with most infections resolving without hospitalization; however, certain groups, including immunocompromised individuals, pregnant people, and those with unresolved skin conditions, remain at increased risk for more serious illness.