Mpox

Mpox (monkeypox) is a zoonotic virus (animal-to-human transmission) endemic in parts of Central and West Africa. It is caused by the mpox virus which belongs to the orthopoxvirus genus of the Poxviridae family. mpox can be transmitted human-to-human by close contact with skin lesions, body fluids, respiratory droplets, and contaminated materials. There is emerging evidence around presence in semen, but uncertainty about this as a form of transmission.

There are two clades of mpox, Clades I and II. The case fatality ratio for the Clade II has been documented to be around 1%, whereas for Clade I, it may be as high as 10%.

In the 2022 global outbreak of mpox, the first case was identified in the United Kingdom on 7 May 2022 in a recent traveller from Nigeria. At the time of writing on 31 October 2022, global case numbers were over 70,000 confirmed cases across more than 100 countries.

Most cases within this outbreak are men who have sex with men (MSM) with no travel history to Central or West Africa. The 2022 outbreak has been of the less severe Clade II mpox virus.

Mpox classically presents with a prodrome with fever, aches and lymphadenopathy, followed by a characteristic centrifugal rash with the lesions first appearing on the face and moving to distal extremities. The rash also progresses through four stages simultaneously from macules to papules, vesicles then pustules, followed by scabbing.

In the 2022 outbreak, presentations of mpox have been atypical:

• The rash/lesions may be localised to ano-genital skin, or oropharynx or rectal mucosa (proctitis)
• There may be a solitary lesion
• The rash/lesions may not necessarily progress through four stages as described above
• Systemic symptoms may be absent or have developed after the onset of rash.

The clinical presentation is similar to diseases that are more commonly encountered in clinical practice, such as hand foot and mouth disease, varicella zoster, herpes simplex, syphilis and molluscum contagiosum. As a result, more common causes of acute rashes with similar appearances should be considered and excluded where possible.

However, co-infections have occurred sporadically, and given the evolving epidemiology of mpox, patients with a rash suggestive of mpox should be considered for testing, even if other conditions are likely.

For more information of the outbreak please refer to:

• Te Whatu Ora
• Mpox photos and dermatologist advice
• World Health Organization
• United Kingdom
• European Centre for Disease Prevention and Control
• Centers for Disease Control and Prevention
• World Organisation for Animal Health

Clinical criteria

• A clinically compatible illness characterised by the presence of acute unexplained[1] skin and/or mucosal lesions or proctitis (for example anorectal pain, bleeding)
• AND

Epidemiological criteria

At least one of the following:

• exposure[2] to a confirmed or probable case in the 21 days before symptom onset
• is a priority group for testing
• at this time priority groups for testing include the following:
  • persons who had multiple[3] or anonymous sexual partners in the 21 days before symptom onset
  • gay, bisexual or other men who have sex with men (MSM)
• history of travel to a country where mpox is endemic[4] in the 21 days before symptom onset.

Laboratory definitive evidence for a confirmed case requires mpox virus detection by NAAT.

Testing should be limited only to patients who meet the clinical and epidemiological criteria. Laboratory confirmation requires the detection of mpox virus nucleic acid by PCR from an appropriate clinical sample. Local laboratories are to test for Varicella (chickenpox, VZV), Herpes simplex (HSV), +/- syphilis if there is capability, prior to referral to a reference laboratory for mpox testing.

Potential cases are most likely to present to sexual health, primary care, or emergency departments, where the treating physician will collect samples. Note that patients should not present to a community collection centre for sampling. Clinicians are advised to follow the most up to date testing advice which can be found on the New Zealand Microbiology Network website.

• Under investigation: A person that has been reported to a Medical Officer of Health, but information is not yet available to classify it as confirmed, probable or not a case.
• Probable: A person who meets the clinical and epidemiological criteria and laboratory confirmation is not possible
• Confirmed: A person with laboratory definitive evidence.
• Not a case: A person that has been investigated and subsequently found not to meet the case definition.

The natural reservoir of mpox virus remains unknown. However, it has been isolated from several African rodents and primates, including the Gambian pouched rat, tree squirrel, rope squirrel and sooty mangabey monkey.

The incubation period is typically 7 to 14 days, with a range of 5 to 21 days. The incubation period may be influenced by the route of transmission, with invasive exposure (eg, contact with broken skin or mucous membrane) having a shorter incubation period than non-invasive exposure. This is why contacts are asked to monitor for symptoms and take precautions for 21 days from exposure.

In Africa, mpox is a zoonosis with transmission typically occurring animal-to-human via rodents.

Mpox virus does not spread easily between people, but it can be transmitted person-to-person by close contact (including sexual contact) with skin lesions, body fluids, respiratory droplets (when masks aren’t worn), and contaminated materials such as bedding. There has been evidence that it is present in semen, but it is uncertain whether it can be transmitted this way.

The infectious period begins with the onset of symptoms, either prodromal or rash. Cases remain infectious until the rash has resolved, and all lesions have formed scabs and fallen off, leaving fresh skin underneath. Cases are not considered infectious prior to the onset of symptoms, however some cases may not be aware of their exact symptom onset date as initial symptoms may be both very subtle and/or not visible.

Mpox is a notifiable infectious disease in Schedule 1 of the Health Act 1956 from Thursday 9 June 2022. Health practitioners are required to notify the Medical Officer of Health on suspicion of a case, prior to collection of any samples. Heads of medical laboratories are required to notify the Medical Officer of Health of any NAAT result positive for mpox virus.

In the event of a case under investigation, probable or confirmed detected within New Zealand, Public Health/the Medical Officer of Health must contact the on-call Communicable Diseases Officer (0800 GET MOH or notifycommdiseases@health.govt.nz). If a case is notified after usual business hours, a Medical Officer of Health may use their discretion as to when they report the case; reporting after usual business hours or awaiting until usual business hours if sufficient information is available ascertain that the risk to public health is low. If after hours, and initial indications suggest risk of potential onward transmission or high-risk factors, then the case should be reported via calling 0800 GET MOH.

One case of mpox identified in New Zealand constitutes an outbreak.

Maintaining the privacy of cases and contacts of mpox is especially important given the 2022 outbreak’s disproportionate impact on the MSM community. Those to whom a mpox case or contact status is disclosed may interpret this information as confirmation the case or contact is a man who has sex with men, or otherwise a member of the LGBTIQA+ community. This could endanger the safety of the case or contact, or cause them reputational, emotional, or financial damage.

Disclosing case or contact status to any third party must therefore be carefully considered, discussed with the case, and weighted proportionally against the risk of transmission.

In addition to Standard Precautions, Contact and Droplet Precautions should be adhered to for physical examination and collecting samples. This includes the use of eye protection, fluid resistant level II R medical mask, fluid repellent gown and gloves. Upgrade mask to an N2/P95 when undertaking procedures involving the oropharynx (oropharyngeal samples) or handling used contaminated linen, clothing, or towels. A medical mask is sufficient for preliminary clinical assessment.

More guidance on infection prevention and control

The interview should include symptom history including onset date, travel history, identification of any high-risk settings, any exposure to a confirmed or probable case, the nature of any contact with a confirmed or probable case, sexual contact, and intimate partners within 21 days of symptom onset, smallpox and mpox vaccination status, and other relevant clinical findings to exclude other common causes of rash. The case should be assessed for risk factors that could cause them to experience more serious disease. These include age (very young children are at greater risk), having or having had a history of severe atopic eczema, being pregnant or recently post-partum, having extensive lesions at an anatomic site that could lead to complications, and being immunocompromised. Where risk factors are present, consider involvement of additional clinicians from a relevant specialty.

While awaiting test results (cases under investigation)

When tested for mpox, the clinician undertaking testing will assess the case’s symptoms, likelihood of mpox infection, and usual activities to inform the restrictions placed on that case while their test result is awaited. The following criteria facilitate this clinical assessment:

Isolation Risk Assessment Criteria – for clinicians conducting mpox testing

Note: Your local Medical Officer of Health is available to discuss this risk assessment if you wish.

All people being tested for mpox must isolate if any of the following criteria apply to them:

1. Where the clinician has a very high index of suspicion that the person has mpox, such as those who are known sexual or intimate contacts of a case, or those who have attended a high-risk setting, such as a sex-on-site venue or festival, during their incubation period.
2. They have oral mucous membrane lesions.
3. They have lesions that are not able to be easily covered – for instance lesions on the face or hands.
4. They have systemic symptoms, including cold or flu symptoms such as fever, body aches, vomiting or diarrhoea.
5. Immunocompromised cases should isolate until they can be assessed by Public Health in collaboration with their usual clinician. Note that a case with HIV who has an undetectable viral load would not be considered immunocompromised in this instance.

Those not required to isolate should be advised:

1. If they develop systemic symptoms, uncoverable or oral lesions while awaiting their test result, they should commence isolation and advise their clinician.
2. To avoid, where possible, all face-to-face contact with people at high risk of serious disease from mpox. This includes being excluded from work or education if their usual activities are likely to bring them into direct skin-to-skin contact with high-risk people. High-risk groups include pregnant people, young children, people with severe atopic eczema, and immunocompromised people.

All people being tested for mpox, regardless of whether they need to isolate, must be advised:

1. To refrain from sexual or intimate activities, including kissing and hugging and all skin-to-skin contact with other people.
2. That they must inform any healthcare setting they plan on attending that they are awaiting the results of a test from mpox prior to attending.

When test results are returned, those with negative test results should be advised they can cease taking additional precautions for mpox (other diagnoses in consideration may require their own precautions). Clinicians are advised of the possibility of false negative results early in the disease course of mpox. Repeat testing may therefore be warranted if the clinician has a high index of suspicion that the case has mpox.

Those who test positive are considered confirmed cases and managed accordingly.

For confirmed or probable cases

The Medical Officer of Health will advise the case on their management plan. Probable and confirmed cases will need to isolate for a minimum of 7 days from the first presence of lesions, and then take other precautions to prevent onward transmission once released from isolation. They must continue taking precautions until they are no longer infectious which is until their lesions have crusted, the scab has fallen off and a fresh layer of skin has formed underneath (symptoms normally last 14–28 days).

In the first seven days from the first presence of lesions, the case is directed to isolate. Isolation means that:

• Where able, cases should sleep in a separate room and limit contact with household members.
• Cases should wear a mask when in the same room as others and cover skin lesions (where possible).
• Cases should not share clothing, bedding, towels and unwashed crockery and cutlery.
• Cases should not go out to public places or venues or attend places of worship.
• Cases must avoid physical contact, particularly sexual contact over this period (including kissing, intimate touching).
• Cases can walk by themselves while keeping a 1 metre distance from others and must wear a mask when leaving the house.
• Cases should avoid close direct contact with animals, including domestic animals, (such as cats, dogs, mice, and other rodents), livestock, and other captive animals, as well as wildlife due to the possibility of human-to-animal transmission.
• All waste, including medical waste, should be disposed of in a safe manner which is not accessible to rodents and other scavenger animals.
• Cases should where possible, avoid use of contact lenses to prevent infection of the eyes. Where this is not possible, ensure hands are thoroughly washed prior to touching lenses or eyes, and that there are no open lesions on hands (cover these where present).
• Cases should avoid shaving areas where mpox lesions/rash are present.
• Cases should not donate blood, cells, tissue, breast milk, semen, organs, or faeces.
• Cases should avoid contact with people who are at risk of serious disease, including immunocompromised people, children, people with a history of severe atopic eczema, and pregnant people. If this is not possible with the case’s living situation, this should be escalated to the Medical Officer of Health.

Staged Release from Isolation

Phase One

From day 8 onwards, the Medical Officer of Health will assess whether the case should remain in isolation or whether they can leave isolation with precautions. Such assessments must consider:

• Occupation and workplace environment: presence of and contact with people at high risk of serious disease from mpox, ability to work from home, physical distancing at workplace ability, etc.

The following clinical criteria must be met for phase one release:

• At least 7 days since first rash/lesion onset
• No new lesions for 48 hours
• No oral / oral mucous membrane lesions, or all oral / oral mucous membrane lesions completely healed (i.e., scab has fallen off and fresh skin has formed underneath)
• No fever or other systemic symptoms due to mpox for 72 hours
• All lesions on exposed skin (i.e., hands, arms, face) have scabbed over, the scab has fallen off and fresh skin has formed underneath, or can adequately cover any unhealed lesions with a dressing and/or clothing
• Not immunocompromised (note that a case with HIV who has an undetectable viral load would not be considered immunocompromised). Immunocompromised cases to be managed on a case-by-case basis with their treating clinician.

If the Medical Officer of Health is satisfied that the public health risk posed by the case leaving isolation is very low, after considering the above factors, the case can leave isolation with additional precautions to prevent transmission. This means:

• Cases can return to work if deemed safe to do so by the Medical Officer of Health
• Cases can leave the house for essential activities, including to buy groceries, medicines, or for solo exercise outdoors.
• Whenever leaving the home, cases must ensure all lesions are covered, (wear a mask if oral lesions present), and avoid close contact with others.
• Cases should avoid all high-risk settings, including early childhood education, gyms, schools.
• Cases must inform healthcare providers of their diagnosis prior to visiting so that appropriate safeguards can be put in place for staff and other patients.
• Cases should avoid public transport where possible.

If new symptoms develop after the first phase of isolation release which cause the Medical Officer of Health to believe there is a greater risk to public health posed by the case being out of isolation, the case may be placed back into isolation. It is anticipated this will be rare and exceptional.

Phase Two

Cases can be fully released from management when all lesions have crusted, scabs have fallen off and a fresh layer of skin has formed underneath.

The Medical Officer of Health will advise on release from isolation, which requires confirmation from a clinician that all lesions are healed.

For 3 months following release from isolation, the virus may still be present in semen. Therefore, condom use during sexual activity is recommended where a case’s semen could come into contact with another person.

Most cases are mild and self-limiting with people recovering within two – four weeks. Most cases will not require specific treatment other than supportive management or treatment of complications (eg, antibiotics for secondary cellulitis).

Advice on clinical management should be sought from an infectious diseases or sexual health physician. Refer to the healthcare pathways for mpox.

Advise the case of the nature of infection and mode of transmission. Educate cases regarding isolation requirements and high-risk people, activities, and settings to avoid while infectious.

Specific support for MSM and others within the rainbow community can be sought from OutLine, the Burnett Foundation, and a full list of support services for rainbow communities can be found on the Rainbow Youth website. Sexual health support and information is available on the Just the Facts website.

Contacts can be separated into three groups: high risk close contacts, moderate risk close contacts, and casual contacts. The local Medical Officer of Health (or local public health or sexual health service) will assess contacts and categorise them based on their exposure to the case.

See Annex, Table 1: Summary of contact tracing definitions and Table 2: Summary of contact management

Close contact - high risk

A high-risk close contact is defined as any person with one or more of the following exposures to a probable or confirmed mpox case:

• Direct physical contact with skin or mucous membranes of a case. (i.e., skin to skin, skin to mucous membranes, mucous membrane to mucous membrane).
• Direct contact with potentially contaminated materials (bed linens healthcare equipment), crusts from lesions or with bodily fluids from a case

It also includes any household contacts who have had close physical contact with the case or contaminated materials, eg bedding or clothing.

A high-risk healthcare contact is a healthcare worker with one or more of the following exposures without appropriate PPE:

• Direct physical contact with case, case materials, crusts, or bodily fluids; or
• Presence in an enclosed room within 1.5 m of a case during aerosol generating procedures
• Sharps injury (including to cleaning or laboratory staff)

Standard and Transmission-based Precautions should be adhered to. 

More guidance on infection prevention and control

Close contact - moderate risk

A moderate-risk close contact is defined as a person with one or more of the following exposures to a probable or confirmed mpox case:

• Indirect contact in an enclosed poorly ventilated indoor space within 1 meter of a case for more than 3 hours
• People sitting either side of a case on an airplane

It also includes household contacts who have not had any direct physical contact but have spent more than three hours with a case.

A moderate-risk healthcare worker is a healthcare worker who has had the following exposure without appropriate PPE:

• Spillage or leakage of laboratory specimen onto intact skin

Casual contact

A casual contact is defined as a person with one or more of the following exposures, or any unlisted exposure that doesn’t meet the criteria above to a probable or confirmed mpox case:

• Household members who have not spent time with or had direct physical contact with the case or contaminated materials from the case.
• Work colleagues in the same workspace as the case.
• Healthcare workers who were wearing appropriate PPE throughout their interaction with a case.
• People on an airplane with the case, aside from the people sitting on either side of the case.

For identifying potential onward exposures, contact trace from prodrome symptom onset, or 24 hours before rash onset for cases without prodrome. Prioritise contact tracing close contacts and healthcare close contacts, such as recent sexual partners, household contacts, and any healthcare workers not wearing appropriate PPE. Contacts should be assessed for known risk factors that could result in more serious disease with mpox, so that further guidance and/or clinical guidance can be provided as required.

No mpox contacts are required to quarantine unless they develop symptoms.

Symptomatic contacts

Mpox contacts who develop symptoms that could be consistent with mpox[5] are required to isolate. Isolating means staying at home and refraining from sexual activity or other close physical contact with others (including those in the home) until advised by Public Health.

Contacts should notify Public Health as soon as possible once symptoms develop.

Where testing is possible and appropriate given the contact’s symptoms (i.e., presence of one or more lesions), liaison with sexual or primary health providers should be undertaken to arrange priority testing.

Where testing is not possible (e.g., symptoms are consistent with mpox prodrome only), contacts should be advised to isolate until further symptoms develop or all symptoms resolve. Release from isolation is at the discretion of the Medical Officer of Health.

Close Contacts – High risk

Quarantine is not required. Contacts directed to isolate immediately if symptoms develop and contact public health.

Active monitoring[6] of symptoms is undertaken for 21 days following last exposure to the case. If symptoms develop, isolate immediately and contact Public Health for further advice.

Contacts are directed, for 21 days following their last exposure to the case to:

• Wear a mask when around others
• If travelling outside the region/country, to advise public health so their management can be transferred
• Advise public health if they work in healthcare
• Avoid high-risk activities including sexual activity, kissing, and other skin-to-skin contact with others

Vaccination may be considered when available.

Close Contact – Moderate Risk

Quarantine is not required. Contacts directed to isolate immediately if symptoms develop and contact public health.

Passive monitoring (self-monitoring)[7] of symptoms for 21 days. If symptoms develop, isolate immediately and contact Public Health for further advice.

Vaccination may be considered for those at higher risk of serious disease when available.

Casual Contact

No quarantine or routine monitoring. No vaccination considered.

Advise the contact and/or caregivers of the nature of the disease and symptoms to monitor for.

• Alakunle E, Moens U, Nchinda G, Okeke MI. 2020. Monkeypox Virus in Nigeria: Infection Biology, Epidemiology, and Evolution. Viruses 12(11): 1257. https://doi.org/10.3390/v12111257
• Brown K, Leggat PA. 2016. Human Monkeypox: Current State of Knowledge and Implications for the Future. Tropical Medicine and Infectious Disease 1(1): pps. https://doi.org/10.3390/tropicalmed1010008
• Centers for Disease Control and Prevention. 2022. Monkeypox: how it Spreads. Available from https://www.cdc.gov/poxvirus/monkeypox/transmission.html
• Communicable Diseases Network Australia. 2022. Monkeypox Virus Infection: CDNA Interim National Guidelines for Public Health Units: Version 2.0. Available from https://www.health.gov.au/resources/publications/monkeypox-virus-infection-cdna-national-guidelines-for-public-health-units
• European Centre for Disease Prevention and Control. 2022. Factsheet for health professionals on monkeypox. Available from https://www.ecdc.europa.eu/en/all-topics-z/monkeypox/factsheet-health-professionals
• Health Protection Surveillance Centre. 2022. Interim Public Health Guidance for the Management of Monkeypox Cases and their Contacts: Version 1.9. Available from: https://www.hpsc.ie/a-z/zoonotic/monkeypox/guidance/Public%20Health%20Advice%20for%20Monkeypox%20Infection%20advice%20for%20confirmed%20cases%20and%20close%20contacts.pdf
• Miura F, van Ewijk CE, Backer JA, Xiridou M, Franz E, Op de Coul E, et al. 2022. Estimated incubation period for monkeypox cases confirmed in the Netherlands. Eurosurveillance 27(24): 2200448. https://doi.org/10.2807/1560-7917.ES.2022.27.24.2200448
• Nolen LD, Osadebe L, Katomba J, Likofata J, Mukadi D, Monroe B, et al. 2016. Extended Human-to-Human Transmission during a Monkeypox Outbreak in the Democratic Republic of the Congo. Emerging Infectious Diseases 22(6): 1014-21. https://doi.org/10.3201%2Feid2206.150579
• UK Health Security Agency. 2022. Guidance Principles for monkeypox control in the UK: 4 nations consensus statement. Available from https://www.gov.uk/government/publications/principles-for-monkeypox-control-in-the-uk-4-nations-consensus-statement/principles-for-monkeypox-control-in-the-uk-4-nations-consensus-statementhttps://www.gov.uk/government/publications/principles-for-monkeypox-control-in-the-uk-4-nations-consensus-statement/principles-for-mpox-control-in-the-uk-4-nations-consensus-statement
• World Health Organization. 2022. Clinical management and infection prevention and control for mpox: Interim rapid response guidance, 10 June 2022. Available from https://www.who.int/publications/i/item/WHO-MPX-Clinical-and-IPC-2022.1
• World Health Organization. 2022. Disease Outbreak News; Multi-country outbreak of mpox, External situation report #2. Available from https://www.who.int/publications/m/item/multi-country-outbreak-of-monkeypox--external-situation-report--2---25-july-2022
• World Health Organization. 2022. Mpox. Available from: https://www.who.int/news-room/fact-sheets/detail/monkeypoxhttps://www.who.int/news-room/fact-sheets/detail/mpox

[1] More common causes of acute rashes with similar appearances should be considered and excluded where possible; varicella zoster, herpes simplex, syphilis, molluscum contagiosum. 

[2] Exposure: direct physical contact with skin or skin lesions, including sexual contact; or contact with contaminated materials such as clothing, bedding, or utensils; or prolonged face-to-face contact, including health care workers without appropriate PPE.

[3] Two or more

[4] Per WHO

[5] These symptoms include: Any Rash, lesions, sores, blisters, or other skin changes not due to other known causes; Headache; Fever; Lymphadenopathy (any lumps or swelling around the neck, armpits, or groin); Myalgia (muscle aches & pains); Arthralgia (joint stiffness); Backache; Rectal pain, discharge, or constipation

[6] Active monitoring for symptoms is when public health officials are responsible for contacting (i.e., by phone, email, text) periodically to see if a person under monitoring has signs/symptoms. The individual under monitoring must take their temperature daily, watch for signs/symptoms compatible with mpox, and immediately isolate and report to public health officials if they have signs/symptoms. If initial symptoms (other than a rash) they should be quarantined and watched closely over the following seven days. If no rash develops, they can return to temperature monitoring for the remaining days. Completion of monitoring will be based on a high trust model. If a contact reports no presentation of rash for 21 days since last close contact exposure to the case (while infectious), they will be released from follow-up.

[7] Self-monitoring for symptoms may be advised for low-risk contacts. Self-monitoring is when the person being monitored is responsible for taking their temperature once daily and watching for signs/symptoms compatible with mpox. The individual should immediately isolate and report to public health officials if they have such signs/symptoms within 21 days of last exposure. If initial symptoms (other than a rash) they should be quarantined and watched closely over the following seven days. If no rash develops, they can return to temperature monitoring for the remaining days.