Monkeypox

Monkeypox is a viral zoonotic disease caused by infection with monkeypox virus that occurs primarily in tropical rainforest areas of Central and West Africa and is occasionally exported to other regions. Monkeypox virus belongs to the Orthopoxvirus genus in the family Poxviridae.

What is monkeypox?

Monkeypox is a viral zoonotic disease caused by infection with monkeypox virus that occurs in animals primarily in tropical rainforest areas of Central and West Africa and is occasionally exported to other regions. Monkeypox virus belongs to the Orthopoxvirus genus in the family Poxviridae.

The Orthopoxvirus genus also includes variola virus (which caused smallpox, an eradicated disease), vaccinia virus (used in the smallpox vaccine), and cowpox virus.

In areas where monkeypox is endemic in animals, the virus is thought to be maintained in nature through circulation among a number of susceptible mammals, namely wild rodents (including squirrels and rats), with occasional spill-over to non-human primates and humans.

Monkeypox has been reported in animals outside of endemic areas, in imported primates, and in pet prairie dogs (rodents of the genus Cynomys) where infection was initially introduced to North America through imported rodents.

More recently monkeypox infection was reported in a pet domestic dog (genus Canis) most likely as a result of human to animal transmission following close direct contact with its owners who were symptomatic with monkeypox. This was the first documented case of human to animal transmission of monkeypox virus.


How is monkeypox transmitted?

Transmission of monkeypox virus can occur when a person or susceptible animal comes into contact with the virus from an animal, human, or materials contaminated with the virus. The virus enters the body through skin lesions (even if not visible to the naked eye), respiratory tract, or mucous membranes.

Monkeypox virus is transmitted from infected animals to humans or other susceptible animals by direct inoculation via bites, scratches or by direct contact with the body fluids and/or the meat of an infected animal during hunting and other activities involving susceptible animal species.

Human-to-human transmission occurs mainly through close physical contact (e.g., face-to-face, skin-to-skin, mouth-to-mouth, mouth-to-skin contact including during sex). Ulcers, lesions or sores present in the mouth or throat can be infectious, meaning the virus can spread through saliva and respiratory droplets (and possibly short-range aerosols), in some cases. More studies are needed on whether the virus can spread from breathing and talking.

Human to animal transmission has been reported in cases of pet dogs which had close contact with their owners who were symptomatic. The dogs showed mucocutaneous lesions and tested positive on PCR.

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Can animals be affected?

Various wild mammals have been identified as susceptible to monkeypox virus. This includes rope squirrels, tree squirrels, Gambian pouched rats, dormice, non-human primates, among others. Although it may depend on the route of transmission and infectious dose, some species are asymptomatic, especially species suspected of being reservoirs (rodents). Other mammals, such as monkeys and great apes, show skin rashes similar to those experienced by humans.

Monkeypox infection has also been reported in pet prairie dogs (rodents of the genus Cynomys), which were initially infected by imported rodents, and most recently in a pet domestic dog (genus Canis) as a result of human to animal transmission.


What is WOAH doing?

WOAH is working with its experts and partners, such as WHO, to gather the latest scientific information and reports from the field. WOAH collates this information and shares it transparently with its members and the general public, aiming to help decision makers to make risk-based decisions considering the latest scientific evidence and avoid unnecessary barriers to trade.


What to do when coming across a suspected animal case?

Notify to WOAH

countries are encouraged to report cases of monkeypox in animals to WOAH as significant animal health information as described in Article 1.1.5 of the Terrestrial Animal Health Code.


Ensure good coordination and communication

using a One Health approach, between wildlife services, veterinary services and public health services.

Use personal protective equipment

including gloves, masks, and disposable protective clothing.

Take samples if possible

for testing for the presence of virus or evidence of exposure to the virus and send them to the national veterinary or reference laboratory (see sample types below).


How to reduce the potential risk of humans infecting animals?

Monkeypox is a zoonotic disease, and there is a risk of spillback to susceptible animals. Therefore, collaboration between public health and veterinary authorities is important when managing the  risk of human to animal transmission. This will help to prevent the disease from being transmitted from humans to susceptible animals at home, in zoos and wildlife reserves, and also to peri-domestic animals, especially rodents.


How can monkeypox virus be detected in animals?

Clinical Signs

The appearance of clinical signs, including the presence of visible skin lesions, is variable and dependent on multiple factors, including the host species, host age, and the monkeypox virus clade.  Detailed clinical signs for individual species can be found by clicking on this link. However, with respect to the monkeypox clade currently circulating in humans, no publicly available clinical or experimental animal susceptibility data is presently available.

In species that present clinical signs of infection with monkeypox virus, animal health professionals should be on the lookout for:

  • Skin lesions (including rashes, papules, pustules, and/or pruritis; affecting part or entire body)
  • Increase in body temperature (pyrexia)
  • Reduced appetite (anorexia)
  • Depression
  • Lethargy
  • Dehydration
  • Oral ulcers
  • Facial edema
  • Conjunctivitis and/or ocular discharge
  • Respiratory signs (including coughing, sneezing, dyspnea, and/or nasal discharge)
  • Abnormal lymph nodes (lymphadenopathy)
  • Diarrhea
Recommended Samples
  • Samples from skin lesions (including scabs)
  • Samples from affected organs (during necropsy)
  • Swabs: conjunctival, oral, nasal, oropharyngeal, and/or anal
  • Scabs
  • Whole blood
  • Serum (for indirect detection or serology)
Recommended Diagnostic Tests
Direct Detection (virus)
  • Polymerase Chain Reaction (PCR, including real-time and conventional) assays * #
  • Loop-mediated isothermal amplification (LAMP) assays*
  • Virus isolation *
  • Electron microscopy *
  • Sequencing *

* Further confirmation by sequencing is recommended, especially when pan-orthopoxvirus PCR or LAMP assays are employed. Whole genome sequencing is encouraged, where possible.
# When available, real-time PCR is preferred to conventional PCR. High genome copy numbers may be expected in suspected monkeypox lesions. Real time PCR positive samples with low genome copy numbers (Ct values above 30) should be reconfirmed by repeat sampling and testing, coupled with additional diagnostic tests, including the analysis of seroconversion.

Indirect Detection (antibodies)
  • Immunofluorescence *
  • ELISA (validated) *
  • Virus Neutralisation Assay *

* Indirect detection is currently restricted to orthopoxvirus specific assays. Testing both acute and convalescent serum samples is recommended. The assays, especially ELISA, should be validated.

Overall Interpretation of Diagnostic Test Results for Confirming Human to Animal Spillback

A monkeypox infection or disease must be confirmed by using a combination of epidemiological features, clinical signs, and suitable diagnostic assays. A suspected monkeypox spillback event (animals getting monkeypox from humans) should satisfy three conditions, including the confirmation of the case (infection or disease) in the human, confirmation of the case in the animal, and the establishment of a confirmed link between the human and the animal case (which could include epidemiological, spatial, temporal, genetic, and seroconversion links, amongst others).

It is recommended that new cases, especially those occurring in new geographical locations or animal species, should be confirmed by a national or international reference laboratory.


What messages should be conveyed to at-risk communities to reduce risk of spillover events?

As a general principle, wash hands after handling wild animals

Take precautions to avoid being bitten or scratched by animals

Avoid contact with susceptible animals

Do not touch wild animals that are sick or have died of unknown causes

Do not eat raw wild animal meat, uncooked or undercooked food, and food made with wild animal blood

Immediately inform the Veterinary or Wildlife Services if you find a sick or dead wild animal

Visit a health centre as soon as possible in case of a scratch or bite from a wild animal

People who are suspected or confirmed to be infected with monkeypox virus should…

…seek medical attention and avoid close direct contact with animals, including domestic pets, livestock, and other captive animals, as well as wildlife.

How do we prevent future monkeypox virus spillovers?

Current outbreaks of monkeypox in humans outside of areas where the virus is known to be endemic in animals appear to be driven by human-to-human transmission.

However, the virus has an animal origin. In areas where the virus is endemic in animals good practices in interacting with wildlife, as described above, can reduce the risk of future spillover events from animals to humans. In fact, these practices should always be followed to avoid risks from a number of pathogens and to protect both humans and wildlife.

To avoid spillover from humans to animals, people who are suspected or confirmed to be infected with monkeypox virus should avoid close direct contact with animals, including domestic animals (such as cats, dogs, hamsters, ferrets, gerbils, etc.), livestock and other captive animals, as well as wildlife. People should be particularly vigilant around animals known to be susceptible, such as rodents, non-human primates etc.

WOAH highlights that unregulated trade in wildlife (including wildlife meat and products) and other mammals can lead to the international spread of diseases such as monkeypox.