Mpox virus

Background

Microbiology

• Mpox virus (MPXV) is in the genus Orthopoxvirus and family Poxviridae

Epidemiology

• Zoonotic disease endemic to west and central Africa
  • Hosts include non-human primates and prairie dogs, squirrels, and possibly other rodents
  • Endemic countries include DRC (most common), Liberia, Ivory Coast, Sierra Leone, Nigeria, Benin, Cameroon, Gabon, and South Sudan
• Human infection is associated with animal trapping, hunting, and skinning, and other exposures to animals including bites, feces, urine, or respiratory droplets
  • Global outbreaks may happen with the global trafficking in exotic pets
• Human-to-human transmission possible, but less than smallpox

Clinical Manifestations

• Clinically indistinguishable from smallpox, though may have much more pronounced lymphadenopathy
• Incubation period about 12 days (possibly up to 21 days)
• Often followed by a prodrome lasting 1 to 4 days of fever, fatigue, headache, and lymphadenopathy (cervical, submandibular, and sublingual)
• Followed by the rash
  • Usually starts on the face and spreads to the body (centrifugal)
  • May involve mucous membranes and genitals, as well as palms and soles
  • Progresses through macules, papules, vesicles, pustules, and finally scabs
    • Classically, well-circumscribed, umbilicated lesions
    • All lesions are at the same stage
  • May be thousands of lesions in unvaccinated patients
• Typically self-resolves over 2 to 4 weeks
• Atypical presentations may include painful genital or oral lesions

Complications

• Mortality 1-10% (per WHO)
• Pitting and scarring
• Secondary bacterial infections
• Pulmonary involvement
• Vomiting or diarrhea with dehydration
• Encephalitis (rare)
• Corneal scarring

Diagnosis

• Swab of a lesion is about 85% sensitive
  • Sensitivity can be increased with 2-3 swabs
• Consider rectal swab if risk factors, regardless of symptoms

Management

• A few antivirals exist that may be helpful1
• Tecovirimat (TPoxx) 600 mg (3x200 mg capsules) p.o. bid for 14 days
  • Specific to Orthopoxviridae
• Cidofovir 5 mg/kg IV once weekly for 2 weeks, possibly followed by same dose every other week
• Brincidofovir 200 mg p.o. once weekly for 2 doses (i.e. day 1 and day 8)

Post-Exposure Prophylaxis

• Can consider using a smallpox vaccine for adults with high risk contact of a confirmed of probable case
• Risk assessment
  • High-risk contact:
    • Community / non-health care setting
      • Household member (e.g., family member, roommate) who lives with and shares indoor common spaces with the case.
      • Close, non-household exposure likely to result in unprotected direct contact to broken skin or mucous membranes including:
        • Intimate or sexual contact;
        • Providing direct physical care without appropriate personal protective equipment (PPE)
        • High risk environmental contact (e.g., cleaning potentially contaminated rooms without wearing appropriate PPE)
    • Health care setting (HCW is the contact)
      • Unprotected contact between an individual’s skin or mucous membranes or bodily fluids from a patient (e.g., accidental splashes of patient saliva to the eyes or oral cavity of a person, contact with patient without appropriate PPE), or contaminated materials (e.g., linens, clothing).
      • Being inside the patient’s room without appropriate PPE, during any procedures that may involve producing aerosols including from:
        • oral secretions (e.g., intubation),
        • skin lesions, or
        • re-suspension of dried fluids (e.g., shaking or changing of soiled linens)
    • Intermediate-risk contact:
      • Community settings: Does not meet high or low risk criteria, but interaction may result in an unprotected exposure to infectious materials (e.g., close, unprotected face-to-face contact, or intact skin-only direct contact).
      • Health-care settings:
        • Health care worker was in the patient care area with close, prolonged contact with an unmasked patient without wearing, at a minimum, a surgical/procedural mask.
        • Actions that result in contact between intact skin or sleeves or other parts of an individual’s clothing and the patient’s skin lesions, bodily fluids, or soiled linens (e.g., turning, bathing, or assisting with transfer) while not wearing appropriate PPE.
    • Low-risk contact:
      • Community settings: no direct physical contact, unlikely droplet exposure
      • Health-care settings:
        • Health care worker was in a patient room without wearing eye protection, regardless of duration of exposure
        • Health care worker wore gown, gloves, eye protection, and a surgical/procedural mask during all visits in the patient care area or room
        • Health care worker was in the patient care area with no close or prolonged contact with an unmasked patient without wearing, at a minimum, a surgical/procedural mask
    • No/very low-risk contact: An exposure deemed not meeting criteria for other risk categories (e.g., transient or brief community interactions that did not involve close or prolonged contact, or risk of direct contact with an infectious lesion)
  • PEP is recommended for high-risk exposures, can be considered for intermediate-risk exposures, and is not recommended for low-/very low-/no-risk exposures
  • PEP is with Imvamune vaccine
    • Accessed through the Public Health units (in Ontario), at EOCoperations.MOH@ontario.ca or 1-866-212-2272