Monkeypox is a rare zoonotic viral disease similar to the now-eradicated human smallpox. The virus belongs to the genus Orthopoxvirus in the family Poxviridae. Variola virus, which is the cause of smallpox, cowpox virus, and vaccinia virus, which is part of the smallpox vaccine, are also from genus Orthopoxvirus. Monkeypox is most prominent in areas of central and west Africa. Though milder than smallpox, it can also be fatal. Wild animals are the most common method of transmission, though the virus can be spread from one person to another.
In 1958, outbreaks of a pox-like disease occurred in two colonies of research monkeys, leading to the discovery of monkeypox. In 1970, the first human case occurred in the Democratic Republic of Congo. Intensive efforts were being made at this time to eradicate smallpox. Monkeypox diagnoses have since been confirmed in central and western African regions. In 2003, the CDC reported 47 cases in the United States, and in 2018, three cases occurred in the United Kingdom, and one in Israel.
Two different genetic groups of monkeypox exist -- Central African and Western African. The Central African virus tends to be more severe in humans than is Western African virus. Fatality rates are higher in humans infected with the Central African variety. Human-to-human transmission of Central African monkeypox virus is well-documented, but there is little evidence of this transmission method for the Western African variety.
The virus enters the body through broken skin, mucous membranes such as the nose, mouth, or eyes, or the respiratory tract. Animal-to-human transmission can come from a scratch or bite, direct contact with an infected animal's bodily fluids, bushmeat preparation, or through direct or indirect contact with lesion material such as an infected animal's bedding. In Africa, people can contract monkeypox by handling infected Gambian giant rats, monkeys, and squirrels. The primary carriers of monkeypox have not yet been identified, but experts believe African rodents play a significant role.
Human-to-human transmission occurs most commonly through large respiratory droplets. Prolonged face-to-face contact is required to transmit monkeypox this way, as respiratory droplets can only travel a few feet. Human-to-human transmission may also occur through direct contact with an infected person's bodily fluids or lesions, or infected clothing or bedding.
The incubation period for monkeypox, the time between infection and the onset of symptoms, ranges from five to 21 days. The symptoms in humans are quite similar to those of symptoms of smallpox but milder. The disease can be divided into two periods -- the invasion period and the skin eruption period. In the invasion period, an individual may have a fever, back pain, severe headaches, muscle aches, and fatigue. Additionally, swelling of the lymph nodes (lymphadenopathy) may occur. This latter symptom is the main difference between the symptoms of monkeypox and smallpox.
Typically, a rash forms one to three days following the appearance of fever in people with monkeypox. The rash usually develops on the face first, before spreading to other parts of the body. A rash on the face is present in 95% of people with the virus, and can also develop on the palms of the hands and soles of the feet. The rash starts as maculopapules, lesions with flat bases. These turn into vesicles, small fluid-filled blisters. The rash evolves into pustules and finally crusts over. This symptom can last from two to four weeks. The number of lesions ranges from only a few to thousands. Severe cases tend to occur most often in young children. The disease is usually self-limiting. In epidemics, the fatality rate is below ten percent.
A medical professional must distinguish monkeypox from other rash illnesses including chickenpox, bacterial skin infections, smallpox (even though it has been eradicated), syphilis, measles, scabies, and medication-related allergic reactions. Special tests are required to definitively diagnose it, so when a doctor suspects the virus, he will send lesion samples to a specific lab.
There are currently no specific treatments available for the virus. However, medical care can effectively control outbreaks. Those who have been vaccinated against smallpox previously may experience milder symptoms of monkeypox than those who never received the vaccine. The spread is controlled through treatments of antivirals, vaccinia immune globulin (VIG), and the smallpox vaccine.
Individuals in areas where monkeypox is endemic can protect themselves by avoiding contact with primates and rodents. Protective clothing, such as gloves, should be worn when handling sick animals, and people should ensure meat is cooked thoroughly before consumption. To reduce the risk of getting monkeypox through human-to-human transmission, people should avoid contact with infected individuals and ensure their skin and faces are covered when caring for the sick.
Healthcare workers who are caring for individuals with suspected or confirmed monkeypox or handling specimens from them should consider getting a smallpox vaccine. Healthcare workers should also wear appropriate protective clothing when caring for infected individuals and wash their hands thoroughly after caring for ill people and handling specimens.