Causes

Mpox  virus is an Orthopox virus closely related to the variola (smallpox) virus. MPX cases previously had been largely confined to endemic areas of Central and West Africa. 
Since May 2022 there has been a global outbreak of MPX across non-endemic regions, mainly among men who have sex with men (MSM). The World Health Organization has declared the MPX outbreak a global health emergency. Studies have shown that among MSM oral and anal shedding is common, as is detection in semen. 

Clinical presentation

The incubation period is 5–21 days, median 7 days. MPX illness may begin with a prodrome of swollen lymph nodes, fever, headache, muscle aches, joint pain and back pain, followed by a rash within 1–3 days after fever onset. Among MSM the rash is disseminated and can concentrate on the following areas: genital, perianal/rectal and oral/perioral. The illness may also present without prodromal symptoms.  

The evolution of skin lesions progress through four stages: macular, papular, vesicular, and pustular, before scabbing over, taking up to four weeks to resolve, from prodrome onset, but averages 10 days (interquartile range: 7-13 days).  

MPX is usually self-limiting, and most people recover within a few weeks; however, complications can occur. 

Complications 

Complications are common (10 -13%) and if severe may require hospitalisation: 

  • Painful ulceration from coalescing lesions: may involve genital, anal and oral areas 
  • Cellulitis from bacterial superinfection 
  • Proctitis with rectal ulcers. There may or may not be perianal lesions 
  • Pneumonia 
  • Encephalitis 
  • Abscesses 
  • Prostatitis 
  • Sepsis 
  • Penile oedema with paraphimosis or phimosis 

The risk of severe disease and complications such as secondary infection, sepsis, pneumonia and encephalitis is increased in people who are immunocompromised, young children and pregnant women. 

Further information regarding clinical features and case definitions can be found in the Alfred Health Mpox Guideline via this link: Alfred Health Mpox Guidelines  

Indication for hospitalisation 

Indications for hospital admission include: 

  • Systemic complications 
  • Severe pain (oral, genital or anorectal) not controlled with oral analgesia 
  • Extensive lesions  
  • Proctitis with severe pain preventing defaecation or bleeding. 
  • Bacterial superinfection with cellulitis needing intravenous antibiotics. 
  • Abscess formation 

Diagnosis

A swab for Mpox pcr should be taken from skin or mucosal lesions. A multiplex pcr also including HSV and syphilis pcr should be taken from genital or anal lesions. The swab is taken from the base of the ulcer.  If there is a vesicle or pustule this should be carefully deroofed.  

Lesions may be present at the following locations: 

Any area of skin including: face and head, torso, limbs 
Oral: oral mucosa including tonsils and tongue, lips, perioral skin 
Anorectal: perianal, rectal mucosa 
Genitals: penis, pubic area, scrotum 

Lesions may join up to form large, painful ulcers. They may be present at one or multiple anatomical locations. 
Systemic symptoms may be present and increase suspicion for MPX.  

Men who have sex with men who have rectal pain (with or without discharge) should have an anal swab for MPX (in addition to anal swabs for gonorrhoea, chlamydia, herpes and syphilis PCR) even if there are no visible perianal lesions. 

Management

Treatment

Perianal or genital ulcer pain:  
Mild cases: paracetamol, non-steroidal anti-inflammatories  
More severe: Panadeine Forte or oxycodone  
Topical lidocaine 

Proctitis with rectal pain:  
Proctosedyl suppositories: can be used up to three times a day for up to 7 days. 
Lactulose or other stool softener 

Bacterial superinfection  
Superinfection with skin bacteria is common and the clinician should have a low threshold for prescribing oral antibiotics. 

Suggested antibiotics are  flucloxacillin, cephalexin, or  Augmentin Duo Forte (particularly with genital or perianal infection) 

Referral to an emergency department is sometimes necessary due to pain or overwhelming infection.  Treatment with antiviral medication such as tecovirimat are  available for severe infection through tertiary hospitals. 

Information for suspected and confirmed cases  

The clinician must provide public health advice to the clients 

  • Avoiding close or intimate contact with others, including all sexual activity. 
  • Keeping exposed lesions covered when around other people. 
  • Wearing a surgical mask if there are oral lesions or respiratory symptoms. 
  • In certain circumstances (based on clinician risk assessment), suspected cases in the following groups should be advised to stay at home: 
    • Those with disseminated disease/unable to cover their lesions. 
    • Those who can’t wear a mask. 
    • Those suspected of having Clade Ib infection. 
  • Local Public Health Units will provide further specific advice regarding requirements to restriction interactions and follow precautions. 

A person with MPX may be infectious from the onset of any symptoms until all scabs in exposed sites have fallen off, leaving intact skin underneath and all systemic symptoms such as fevers, malaise and swollen lymph nodes have also resolved.

1The client should be advised they should use a condom for 12 weeks and not donate any blood, cells, tissue, breast milk, semen or organs. 

MPX sexual contacts 

In Victoria, Local Public Health Units will conduct contact tracing for Mpox cases. Sexual contacts of MPX should be advised to monitor for symptoms for 21 days and seek medical review if they develop symptoms.   

Prevention

Vaccination 

Jynneos is the preferred Mpox vaccine and is widely available.  JYNNEOS is a 3rd generation highly-attenuated vaccine that is replication-deficient.

It is administered in a 2-dose schedule by subcutaneous injection with a minimum dose interval between doses of 28 days. JYNNEOS is associated with fewer potential adverse events and is safe to use in people with immunocompromise or atopic dermatitis.

JYNNEOS may also be used in children or during pregnancy, after risk-benefit assessment.

Jynneos may be used pre-exposure, allowing 2 weeks until effective, or post-exposure to Mpox up to 4 days after exposure. 

Disclaimer

We recognise that gender identity is fluid. In our treatment guidelines, the words and language we use to describe genitals and gender are based on the sex assigned at birth.

The content of these treatment guidelines is for information purposes only. The treatment guidelines are generic in character and should be applied to individuals only as deemed appropriate by the treating practitioner on a case by case basis. Alfred Health, through MSHC, does not accept liability to any person for the information or advice (or the use of such information or advice) which is provided through these treatment guidelines. 

The information contained within these treatment guidelines is provided on the basis that all persons accessing the treatment guidelines undertake responsibility for assessing the relevance and accuracy of the content and its suitability for a particular patient. Responsible use of these guidelines requires that the prescriber is familiar with contraindications and precautions relevant to the various pharmaceutical agents recommended herein.