Mpox

Mpox is a zoonotic disease first discovered in monkeys and in humans in 1970 in the Democratic Republic of the Congo (DRC). However, it has now demonstrated sustained human-to-human transmission. While it mostly occurs in Central and Western African countries close to tropical rainforests, it has been exported as happened in the wave of outbreaks in 2022 across Europe, the Americas, and subsequently up to 110 countries. In 2024, outbreaks have spread to central and east African countries that had never previously reported the disease such as Burundi, Kenya, Rwanda, and Uganda. 

There are two broad clades of the mpox virus: clade I and II (which was behind the global mpox outbreak that began in 2022). It is postulated that clade I leads to more severe disease and death than clade II in the populations where it is endemic. A new offshoot of clade I virus, called clade Ib, which was first reported in the DRC in 2023 and spread through close contact, including sexual contact, is implicated in the 2024 epidemic.

In light of this, WHO in August 2024, determined that mpox a public health emergency of international concern (PHEIC) under the International Health Regulations (2005) (IHR) - the second mpox PHEIC in 2 years.

Available data indicates that case fatality rate for mpox can be as high as 10%. This may may differ in different settings due to several factors, such as access to health care and underlying immunosuppression such as  HIV disease.

The following are standard case definitions to allow national health authorities to interpret data in an international context. However, during an outbreak, case definitions may be adapted to the local context and the Red Cross Red Crescent should use those agreed/established by national health authorities. NB: Consider that during community surveillance, volunteers should use broad (simplified) case definitions to recognize most or all possible cases and encourage them to seek care. Other actors such as healthcare workers or investigators studying the cause of a disease, on the other hand, can use more specific case definitions that may require laboratory confirmation.

Clinical criteria: acute skin rash or lesions, fever (subjective or measured temperature of over 38.5° C [101.3° F], other clinical signs and symptoms (chills and/or sweats, headache, backache, muscle ache, lymphadenopathy, sore throat, cough, shortness of breath and fatigue).

Epidemiologic criteria: exposure to an exotic or wild mammalian pet with clinical signs of illness (e.g. conjunctivitis, respiratory symptoms, and/or rash) OR exposure to an exotic or wild mammalian pet with or without clinical signs of illness that has been in contact with either a mammalian pet or a human with mpox OR exposure to a suspect, probable, or confirmed human case of mpox.

Laboratory criteria: isolation of mpox virus in culture OR demonstration of mpox virus DNA by polymerase chain reaction (PCR) testing of a clinical specimen OR demonstration of virus morphologically consistent with an orthopoxvirus by electron microscopy in the absence of exposure to another orthopoxvirus OR demonstration of presence of orthopoxvirus in tissue using immunohistochemical testing methods in the absence of exposure to another orthopoxvirus.

Case classification

Suspect case: meets one of the epidemiologic criteria AND fever or unexplained rash/lesions AND two or more other signs or symptoms with onset of first sign or symptom less than 21 days after last exposure meeting epidemiologic criteria.

Probable case: meets one of the epidemiologic criteria AND fever AND acute skin rash, mucosal lesions or lymphadenopathy, OR if rash is present but the type is not described, OR vesicular-pustular rash with onset of first sign or symptom less than 21 days after last exposure to a probable or confirmed mpox case, OR has had multiple and/or casual sexual partners within the 21 days before symptom onset, OR positive test result for orthopoxviral infection using OPXV-specific PCR   and it demonstrates elevated levels of IgM antibodies reactive with orthopoxvirus between at least days 7 to 56 after rash onset.

Confirmed case: lesion samples/materials contain unique sequences of viral DNA detected through real-time polymerase chain reaction (PCR) and/or sequencing.

WHO case definition and classification source of information: 

WHO Mpox (Monkeypox) outbreak toolbox

https://www.cdc.gov/poxvirus/mpox/veterinarian/mpox-in-animals.html 

WHO laboratory testing information: 

Diagnostic testing for the monkeypox virus (‎MPXV)‎: interim guidance, 10 May 2024

Single case 

• People in close contact with infected persons via skin-to-skin (such as touching or anal/vaginal sex) mouth-to-mouth, or mouth-to-skin (such as kissing the skin or oral sex) as well as face-to-face (including talking or breathing in close proximity).
• People in constant contact with clothing, bedding, towels, objects, electronics and other surfaces touched by an infected person
• People with multiple and/or casual sexual partners. It is important to note that during the global outbreak that began in 2022, the virus mostly spread through sexual contact.
• Men who have sex with men are also at risk
• People in close contact with infected animals (including the animal’s blood and other bodily fluids).
• Eating inadequately cooked meat of infected animals.
• No proper sanitation and hygiene measures.
• Caregivers and healthcare workers in close contact with infected people when infection control precautions are not strictly practiced.

Attack rates will vary from one outbreak to another. In case of an outbreak, consult the latest information provided by health authorities.

3—28 per cent in recent outbreaks among close contacts.

• Infection is more severe and mortality is higher among children and young adults.
• Immunosuppressed persons such as those receiving chemotherapy, transplant recipients or HIV carriers.
• People with chronic diseases such as renal disease, cancer, chronic lung or liver disease and diabetes.
• People who have multiple or new sexual partners are most at risk. Gay, bisexual and other men who have sex with men may be at higher risk of being exposed if they have sex or other form of close contact with someone who is infectious.  

Mpox virus 

Zoonotic disease: The natural reservoir of mpox viruses is not identified. Hosts include many animals such as rope squirrels, tree squirrels, Gambian rats, striped mice, dormice, prairie dogs, marmots and groundhogs, chinchillas, hedgehogs, shrews, and primates.

• Contact transmission: Primarily transmitted to people through direct contact with the blood, body fluids, or cutaneous or mucosal lesions of infected persons or of infected animals (monkey, prairie dogs, rats, squirrels, and others), through  bite or scratch. Human-to-human transmission can also occur through contact with the infected person’s skin, mouth or  contaminated objects (e.g. bedding) of an infected person.
• Vehicle-borne transmission: Eating inadequately cooked meat of infected animals is a possible risk factor.
• Droplet spread: Human-to-human transmission is also possible via respiratory droplets usually requiring prolonged face-to-face contact.
• Mother-to-child transmission can also occur during or after birth.

6—16 days (range 1—21 days).

First week of rash.

• The clinical presentation is similar to the eradicated disease smallpox.
• The invasion period (0—5 days) is characterized by fever, intense headache, swelling of the lymph nodes, back pain, muscle ache and an intense lack of energy.
• The skin eruption period (within one to three days after the appearance of fever) where the various stages of the rash appear, often begins on the face and then spreads elsewhere on the body. The face (in 95 per cent of cases), and palms of the hands and soles of the feet (in 75 per cent of cases) are most affected. Evolution of the rash from maculopapules (lesions with a flat base) to vesicles (small fluid-filled blisters), pustules, followed by crusts occurs in approximately ten days which may last up to three weeks.
• Some patients develop severe swollen lymph nodes before the appearance of the rash, which is a distinctive feature of mpox compared to other similar diseases.
• Although the clinical manifestation of mpox is milder than that of smallpox, the disease can kill up to 11 per cent of infected people. Complications are respiratory distress, secondary bacterial infections and encephalitis.

Smallpox, varicella (chickenpox), measles, bacterial skin infections, scabies, syphilis and medication-associated allergies.

• Polymerase chain reaction (PCR).
• Virus isolation by cell culture.
• Serology: IgM and IgG antibodies detection by enzyme-linked immunosorbent assay (ELISA). Recommended for use by the WHO at reference laboratories only.

Please refer to the appropriate local or international guidelines for clinical management. All clinical management including the administration of a treatment or vaccine should be conducted by a health professional. 

• There are no specific treatments or vaccines available for mpox infection.
• Early supportive care is advised to manage the symptoms and avoid complications.
• Because mpox virus is closely related to the virus that causes smallpox, the smallpox vaccine can protect from getting mpox. Experts also believe that vaccination after a mpox exposure may help prevent the disease or make it less severe, if given soon after exposure. New and safer vaccines have been approved for the prevention of smallpox and mpox since 2018. Following the worldwide eradication of smallpox, the smallpox vaccine is not available to the general public, but vaccine stockpiles are maintained by several countries and the World Health Organization (WHO).
• Also, antivirals initially developed to treat smallpox including tecovirimat have been used to treat mpox.
• Pre-exposure smallpox vaccination for high-risk groups (e.g. public health workers investigating the outbreak, animal control or veterinarian workers, healthcare and laboratory workers, close contacts without contraindications) has been effective.
• Post-exposure smallpox vaccination (within four days of initial exposure to mpox) can be discussed in outbreak areas.

Past data suggest that the smallpox vaccine is at least 85 per cent effective in preventing mpox.