Monkeypox

An infectious disease caused by the Monkeypox virus of the Orthopoxvirus genus that is endemic in West and Central Africa but has recently spread to the Americas, Europe, and Australia. Monkeypox is usually transmitted by close contact to infected animals (mostly rodents). Human-to-human transmission is rare but becoming more common. Clinical features include flu-like symptoms, lymphadenopathy, and a painful, vesicular rash that typically develops within 1–3 days after the onset of fever. Diagnosis is confirmed by PCR from lesion exudate. Affected individuals generally recover within 2–4 weeks with supportive treatment. A monkeypox and smallpox live vaccine (Jynneos) was approved for adults in the US in 2019.

• Endemic in West and Central Africa ^[1]
• Travel-associated outbreak in the UK in May 2022, with subsequent cases in continental Europe, North America, South America, and Australia. ^[2]
• On July 23, 2022, the WHO declared the monkeypox outbreak a public health emergency of international concern. ^[3]

Epidemiological data refers to the US, unless otherwise specified.

• Pathogen: Monkeypox virus (dsDNA virus of the Orthopoxvirus genus in the family Poxviridae)
• Reservoir: rodents, apes, monkeys, humans ^[4]
• Transmission
  • Human-to-human transmission
    • Contact and sexual transmission through cutaneous or mucosal lesions and/or body fluids (e.g., sex, kissing, hugging, massaging)
    • Respiratory droplet transmission
    • Vertical transmission
    • Fomite transmission (e.g., from contaminated clothes, bed sheets)
    • High risk groups include:
      • Men who have sex with men
      • Individuals with multiple sex partners
      • Sex workers
      • Health care workers (e.g., emergency room staff)
  • Animal-to-human transmission: scratch or bite from an infected animal
• Incubation period: 5–21 days ^[1]

• Prodrome: 1–3 days
  • Flu-like symptoms
  • Lymphadenopathy
• Dermatological lesions: painful, blistering rash with ingrained, hard, well-circumcised ulcerations (2–4 weeks)

Similar-looking blistering diseases such as chickenpox and smallpox typically do not cause lymphadenopathy.

• PCR of lesion exudate

• Chickenpox
• Smallpox
• Measles
• Syphilis
• Autoimmune blistering diseases
• Herpes zoster
• Scabies

The differential diagnoses listed here are not exhaustive.

• General principles ^[5]
  • Isolation at home
  • Caution while using shared surfaces (e.g., in the kitchen and bathroom)
  • Cleaning used bed sheets
• Management of individuals with mild and/or uncomplicated disease ^[5]
  • Antipyretics and analgesia as needed (e.g., acetaminophen, ibuprofen)
  • Rest, adequate hydration, and nutrition
  • Conservative treatment of the rash to relieve symptoms and prevent complications, including bacterial superinfection (for further information see also “Overview of treatment of dermatological diseases”)
• Management of individuals with a high risk of complications (i.e., young children, pregnant women, and immunosuppressed individuals) and/or severe disease ^[5]
  • Management as in mild and/or uncomplicated disease
  • Admission to the hospital for close monitoring
  • Antiviral therapy ^[6]
    • Tecovirimat
    • Possible alternatives for treatment: cidofovir or brincidofovir

• Bronchopneumonia
• Encephalitis
• Bacterial superinfection
• Sepsis
• Blindness following infection of the cornea

We list the most important complications. The selection is not exhaustive.

• Affected individuals typically recover within 2–4 weeks. ^[1]
• Mortality: 1–10% (esp. children and immunocompromised individuals)

• Vaccination ^[7]
  • A monkeypox and smallpox live vaccine (Jynneos) was approved for adults in the US in 2019.
  • The small pox live vaccine (ACAM2000) provides ∼ 85% protection against monkeypox virus.
  • Postexposure prophylaxis
    • Within 4 days after first exposure
    • If given 4–14 days after first exposure vaccine may mitigate symptoms but does not prevent the disease
  • Preexposure prophylaxis
    • Laboratory workers working with orthopoxviruses
    • Certain health care workers at risk (e.g., emergency room staff)
• Sexual activity control ^[5]
  • Sexual abstinence until all crusted lesions have healed
  • Consistent use of condoms for at least 12 weeks after recovery