Monkeypox

OVERVIEW

• Viral zoonotic infection
• Incubation period 6-13 days
• Causes rash similar to smallpox
• Person-to-person transmission and mortality is significantly lower than smallpox

TRANSMISSION

• Human-to-human
  • Bodily fluids
  • Cutaneous lesions
  • Respiratory droplets — requires prolonged face-to-face contact
• Animal-to-human (zoonotic)
  • Bodily fluids
  • Cutaneous lesions

CLINICAL FEATURES

The majority of infections are asymptomatic.

Symptomatic infection can be divided into two phases:

1. Invasion period

• Fever
• Myalgia
• Headache
• Lymphadenopathy (distinguishing feature from smallpox) — submandibular, cervical, inguinal

2. Skin eruption period (1-3 days after fever) causes a characteristic rash

• Initially maculopapular
• Transiently starts on trunk and spreads peripherally to face, palms, and soles of feet
• Progresses over 2-4 weeks to vesicles, pustules, followed by scabbing and desquamation
• Localised rash on hand(s) can occur following direct contact with infected animal or human

INVESTIGATIONS

• Viral PCR

DIFFERENTIAL DIAGNOSIS

• Varicella (chickenpox)
  • Vesicular lesions in varicella are often in different stages of development and healing
  • This differs from monkeypox, where lesions are generally all at the same stage

• Smallpox
  • Lymphadenopathy is a key distinguishing feature of monkeypox

• Eczema herpeticum
• Measles
• Scabies
• Drug rash

MANAGEMENT

Management is generally supportive. Most symptomatic patients have mild self-limiting disease.

More severe cases or immunocompromised patients may require specific antiviral treatment:

• Cidofovir — no clinical data for efficacy in humans, can cause nephrotoxicity
• Tecovirimat
• Brincidofovir (analogue of cidofovir)

COMPLICATIONS

• Secondary skin infection
• Bronchopneumonia
• Sepsis
• Encephalitis
• Corneal infection with ensuing visual loss

Mortality has historically ranged from 0-10%. Only three previous outbreaks have occurred:

• Central Africa 1996-1998, mortality ~10%
• USA 2003, mortality 0%
• Nigeria 2017-present (~200 confirmed cases), mortality 3%

References

Tweetorials

• BK Titanji. July 18, 2021
• Tessa Davis. May 19, 2022
• John Ross. May 19, 2022
• Angela Rasmussen. May 19, 2022

Guidelines

• Nickson C. Monkeypox – CCC. LITFL
• Monkeypox. Centers for Disease Control and Prevention
• Monkeypox: Guidance. UK Health Security Agency

Publications

• Fleischauer AT et al. Evaluation of Human-to-Human Transmission of Monkeypox from Infected Patients to Health Care Workers. Clinical Infectious Diseases, 2005; 40(5): 689–694
• Macneil A et al. Transmission of atypical varicella-zoster virus infections involving palm and sole manifestations in an area with monkeypox endemicity. Clin Infect Dis. 2009 Jan 1;48(1):e6-8.
• Verreault D, Killeen SZ, Redmann RK, Roy CJ. Susceptibility of monkeypox virus aerosol suspensions in a rotating chamber. J Virol Methods. 2013 Feb;187(2):333-7.
• Brown K, Leggat PA. Human Monkeypox: Current State of Knowledge and Implications for the Future. Trop Med Infect Dis. 2016 Dec 20;1(1):8.
• Sklenovská N, Van Ranst M. Emergence of Monkeypox as the Most Important Orthopoxvirus Infection in Humans. Front Public Health. 2018 Sep 4;6:241.
• Petersen E et al. Monkeypox – Enhancing public health preparedness for an emerging lethal human zoonotic epidemic threat in the wake of the smallpox post-eradication era. Int J Infect Dis. 2019 Jan;78:78-84
• Beer EM, Rao VB. A systematic review of the epidemiology of human monkeypox outbreaks and implications for outbreak strategy. PLoS Negl Trop Dis. 2019 Oct 16;13(10):e0007791. doi: 10.1371/journal.pntd.0007791
• Alakunle E, Moens U, Nchinda G, Okeke MI. Monkeypox Virus in Nigeria: Infection Biology, Epidemiology, and Evolution. Viruses. 2020 Nov 5;12(11):1257.