Mpox (monkeypox)

Overview

Mpox (monkeypox) is an infectious disease caused by the monkeypox virus. It can cause a painful rash, enlarged lymph nodes and fever. Most people fully recover, but some get very sick.

Anyone can get mpox. It spreads from contact with infected:

• persons, through touch, kissing, or sex
• animals, when hunting, skinning, or cooking them
• materials, such as contaminated sheets, clothes or needles
• pregnant persons, who may pass the virus on to their unborn baby.

If you have mpox:

• Tell anyone you have been close to recently
• Stay at home until all scabs fall off and a new layer of skin forms
• Cover lesions and wear a well-fitting mask when around other people
• Avoid physical contact.

The disease mpox (formerly monkeypox) is caused by the monkeypox virus (commonly abbreviated as MPXV), an enveloped double-stranded DNA virus of the Orthopoxvirus genus in the Poxviridae family, which includes variola, cowpox, vaccinia and other viruses. The two genetic clades of the virus are clades I and II.

The monkeypox virus was discovered in Denmark (1958) in monkeys kept for research and the first reported human case of mpox was a nine-month-old boy in the Democratic Republic of the Congo (DRC, 1970). Mpox can spread from person to person or occasionally from animals to people. Following eradication of smallpox in 1980 and the end of smallpox vaccination worldwide, mpox steadily emerged in central, east and west Africa. A global outbreak occurred in 2022–2023. The natural reservoir of the virus is unknown – various small mammals such as squirrels and monkeys are susceptible.

Transmission

Person-to-person transmission of mpox can occur through direct contact with infectious skin or other lesions such as in the mouth or on genitals; this includes contact which is

• face-to-face (talking or breathing)
• skin-to-skin (touching or vaginal/anal sex)
• mouth-to-mouth (kissing)
• mouth-to-skin contact (oral sex or kissing the skin)
• respiratory droplets or short-range aerosols from prolonged close contact

The virus then enters the body through broken skin, mucosal surfaces (e g oral, pharyngeal, ocular, genital, anorectal), or via the respiratory tract. Mpox can spread to other members of the household and to sex partners. People with multiple sexual partners are at higher risk.

Animal to human transmission of mpox occurs from infected animals to humans from bites or scratches, or during activities such as hunting, skinning, trapping, cooking, playing with carcasses, or eating animals. The extent of viral circulation in animal populations is not entirely known and further studies are underway.

People can contract mpox from contaminated objects such as clothing or linens, through sharps injuries in health care, or in community setting such as tattoo parlours.

Signs and symptoms

Mpox causes signs and symptoms which usually begin within a week but can start 1–21 days after exposure. Symptoms typically last 2–4 weeks but may last longer in someone with a weakened immune system.

Common symptoms of mpox are:

• rash
• fever
• sore throat
• headache
• muscle aches
• back pain
• low energy
• swollen lymph nodes.

For some people, the first symptom of mpox is a rash, while others may have different symptoms first.

The rash begins as a flat sore which develops into a blister filled with liquid and may be itchy or painful. As the rash heals, the lesions dry up, crust over and fall off.

Some people may have one or a few skin lesions and others have hundreds or more. These can appear  anywhere on the body such as the:

• palms of hands and soles of feet
• face, mouth and throat
• groin and genital areas
• anus.

Some people also have painful swelling of their rectum or pain and difficulty when peeing.

People with mpox are infectious and can pass the disease on to others until all sores have healed and a new layer of skin has formed.

Children, pregnant people and people with weak immune systems are at risk for complications from mpox.

Typically for mpox, fever, muscle aches and sore throat appear first. The mpox rash begins on the face and spreads over the body, extending to the palms of the hands and soles of the feet and evolves over 2-4 weeks in stages – macules, papules, vesicles, pustules. Lesions dip in the centre before crusting over. Scabs then fall off. Lymphadenopathy (swollen lymph nodes) is a classic feature of mpox. Some people can be infected without developing any symptoms.

In the context of the global outbreak of mpox which began in 2022 (caused mostly by Clade IIb virus), the illness begins differently in some people. In just over a half of cases, a rash may appear before or at the same time as other symptoms and does not always progress over the body. The first lesion can be in the groin, anus, or in or around the mouth.

People with mpox can become very sick. For example, the skin can become infected with bacteria leading to abscesses or serious skin damage. Other complications include pneumonia, corneal infection with loss of vision; pain or difficulty swallowing, vomiting and diarrhoea causing severe dehydration or malnutrition; sepsis (infection of the blood with a widespread inflammatory response in the body), inflammation of the brain (encephalitis), heart (myocarditis), rectum (proctitis), genital organs (balanitis) or urinary passages (urethritis), or death. Persons with immune suppression due to medication or medical conditions are at higher risk of serious illness and death due to mpox. People living with HIV that is not well-controlled or treated more often develop severe disease.

Diagnosis

Identifying mpox can be difficult as other infections and conditions can look similar. It is important to distinguish mpox from chickenpox, measles, bacterial skin infections, scabies, herpes, syphilis, other sexually transmissible infections, and medication-associated allergies. Someone with mpox may also have another sexually transmissible infection such as herpes. Alternatively, a child with suspected mpox may also have chickenpox. For these reasons, testing is key for people to get treatment as early as possible and prevent further spread.

Detection of viral DNA by polymerase chain reaction (PCR) is the preferred laboratory test for mpox. The best diagnostic specimens are taken directly from the rash – skin, fluid or crusts – collected by vigorous swabbing. In the absence of skin lesions, testing can be done on oropharyngeal, anal or rectal swabs. Testing blood is not recommended. Antibody detection methods may not be useful as they do not distinguish between different orthopoxviruses.

More information on laboratory confirmation of mpox can be found here.

Treatment and vaccination

The goal of treating mpox is to take care of the rash, manage pain and prevent complications. Early and supportive care is important to help manage symptoms and avoid further problems.

Getting an mpox vaccine can help prevent infection. The vaccine should be given within 4 days of contact with someone who has mpox (or within up to 14 days if there are no symptoms).

It is recommended for people at high risk to get vaccinated to prevent infection with mpox, especially during an outbreak. This includes:

• health workers at risk of exposure
• men who have sex with men
• people with multiple sex partners
• sex workers.

Persons who have mpox should be cared for away from other people.

Several antivirals, such as tecovirimat, originally developed to treat smallpox have been used to treat mpox and further studies are underway. Further information is available on mpox vaccination and case management.

Self-care and prevention

Most people with mpox will recover within 2–4 weeks. Things to do to help the symptoms and prevent infecting others:

Do

• stay home and in your own room if possible
• wash hands often with soap and water or hand sanitizer, especially before or after touching sores
• wear a mask and cover lesions when around other people until your rash heals
• keep skin dry and uncovered (unless in a room with someone else)
• avoid touching items in shared spaces and disinfect shared spaces frequently
• use saltwater rinses for sores in the mouth
• take sitz baths or warm baths with baking soda or Epsom salts for body sores
• take over-the-counter medications for pain like paracetamol (acetaminophen) or ibuprofen.

Do not

• pop blisters or scratch sores, which can slow healing, spread the rash to other parts of the body, and cause sores to become infected; or
• shave areas with sores until scabs have healed and you have new skin underneath (this can spread the rash to other parts of the body).

To prevent spread of mpox to others, persons with mpox should isolate at home, or in hospital if needed, for the duration of the infectious period (from onset of symptoms until lesions have healed and scabs fall off). Covering lesions and wearing a medical mask when in the presence of others may help prevent spread. Using condoms during sex will help reduce the risk getting mpox but will not prevent spread from skin-to-skin or mouth-to-skin contact.

Outbreaks

After 1970, mpox occurred sporadically in Central and East Africa (clade I) and West Africa (clade II). In 2003 an outbreak in the United States of America was linked to imported wild animals (clade II). Since 2005, thousands of suspected cases are reported in the DRC every year. In 2017, mpox re-emerged in Nigeria and continues to spread between people across the country and in travellers to other destinations. Data on cases reported up to 2021 are available here.

In May 2022, an outbreak of mpox appeared suddenly and rapidly spread across Europe, the Americas and then all six WHO regions, with 110 countries reporting about 87 thousand cases and 112 deaths. The global outbreak has affected primarily (but not only) gay, bisexual, and other men who have sex with men and has spread person-to-person through sexual networks. More information on the global outbreak is available here with detailed outbreak data here;

In 2022, outbreaks of mpox due to Clade I MPXV occurred in refugee camps in the Republic of the Sudan. A zoonotic origin has not been found.

WHO response

The global outbreak of mpox was declared a public health emergency of international concern (PHEIC) on 23 of July 2022. WHO published a strategic preparedness and response plan for mpox and a suite of technical guidance documents.  Surveillance, diagnostics, risk communication and community engagement remain central to stopping the outbreak and eliminating human-to-human transmission of mpox in all contexts.

More information can be found here. Questions and answers are here and public health advice is here.