Mpox
Mpox is a systemic orthopoxvirus infection transmitted by direct contact with skin lesions or body fluids, producing fever, lymphadenopathy, and a synchronous vesiculopustular rash that evolves through umbilicated papules before crusting. Diagnosis is confirmed by PCR for orthopoxvirus DNA from a lesion swab, and tecovirimat is reserved for severe or high-risk disease while most cases are managed with isolation and supportive care.
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What this article covers
- Overview
Systemic orthopoxvirus illness: mpox (formerly monkeypox) is caused by monkeypox virus, a double-stranded DNA orthopoxvirus that produces a systemic illness with fever, lymphadenopathy, mucosal…
- Epidemiology
Outbreak-associated disease: mpox has caused recognized outbreaks with sustained human-to-human transmission, a pattern distinct from its historical profile as a sporadic zoonosis.
- Risk factors
Direct skin-to-skin or mucosal contact with an infected person: the dominant risk factor, including intimate or sexual contact, given the anogenital predominance of lesions.
- Pathophysiology
Viral entry through skin or mucosa: monkeypox virus enters through breaks in skin or through mucosal surfaces after direct contact with lesion material or body fluids.
- Clinical features
Systemic prodrome: fever, myalgias, headache, and lymphadenopathy typically precede or accompany the onset of the skin eruption; lymphadenopathy is a key discriminating feature from other vesiculopustular illnesses.
- Differential diagnosis
Varicella (chickenpox): vesicles/pustules in varying stages of evolution simultaneously ("crops"), typically without the prominent lymphadenopathy of mpox; Tzanck smear and PCR for varicella-zoster virus distinguish it.
- Diagnosis
Confirmed by PCR for orthopoxvirus DNA from a lesion swab: a diagnosis of mpox is established by PCR testing for orthopoxvirus DNA obtained from a swab of a skin lesion; this is the diagnostic gold standard.
- Management
First, isolate the patient and initiate contact and droplet precautions for the duration of active lesions, since transmission occurs through direct contact with lesion material and body fluids…
- Complications
Secondary bacterial skin infection: breakdown of pustular lesions predisposes to superinfection, which can extend the illness course and risk scarring.
- Prognosis
Generally favorable in immunocompetent hosts: most cases resolve over 2-4 weeks without lasting sequelae beyond potential scarring.
- Prevention
JYNNEOS (modified vaccinia Ankara) vaccine for pre-exposure prophylaxis: administered as a 2-dose series (0.5 mL subcutaneous, or 0.1 mL intradermal for dose-sparing) at day 0 and day 28 for persons at high risk of exposure.
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