Monkeypox

Key Features

• Poxvirus infection with syndrome similar to smallpox

• Incubation period ~13 days (range, 6–28 in one outbreak)

• Mortality 3–11% depending on patient immune status; secondary attack rate ~10%

• Enzootic in equatorial African rain forests, with limited person-to-person spread via exchange of body fluids or via droplets

• Risk factors include rodent bite, working as a hunter, and being male > 18 years of age

• First community-acquired outbreak in the United States occurred in 2003 in upper Midwest, apparently due to imported Gambian giant rats via consequent exposure of prairie dogs; other susceptible animals include nonhuman primates, rabbits, and rodents, including giant pouched rat in Central Africa (US federal agencies prohibit importation of African rodents)

• In May 2022, an outbreak of monkeypox was identified in a number of countries globally that do not typically experience it, including cases in at least 10 states in the United States

• The CDC response can be found at https://www.cdc.gov/poxvirus/monkeypox/response/2022/index.html

Clinical Findings

• Febrile prodrome

• Lymphadenopathy

• Rash distinguished by deep-seated and well-circumscribed nature, lesions at the same stage of development (unlike varicella but like smallpox), and centrifugal progression (including palms and soles)

Diagnosis

• Based on rash and lymphadenopathy (seen in ≤ 90% of unvaccinated persons)

• Local and state public health officials and the CDC should be notified for assistance with confirmation of the diagnosis by

  • Electron microscopy

  • Viral culture

  • ELISA

  • PCR

  • GeneXpert MPX/OPX (monkeypox/orthopox) assay

• Differential diagnosis includes varicella smallpox and varicella, but the rashes are generally distinct

Treatment

• Suspected cases should be placed on standard, contact, and droplet precautions

• No standard or optimized guidelines for the clinical management of monkeypox exist

• Cidofovir is effective in vitro, and its less toxic prodrug brincidofovir may be useful as well

• Vaccinia immune globulin can be used in selected cases

• Postexposure vaccination is advised for documented contacts of infected persons or animals

• More information on treatment can be found at https://www.cdc.gov/poxvirus/monkeypox/treatment.html

• General preventive measures include

  • Avoidance of contact with rodents from endemic areas (whose illness is manifested by alopecia, rash, and ocular or nasal discharge)

  • Appropriate care and isolation of humans exposed to such animals within the prior 3 weeks

  • Veterinary examination and investigation of suspect animals through health departments

• Vaccinia immunization (MVA-BN)

  • Effective against monkeypox

  • Recommended for

    • Adults 18 and older involved in the investigation of an outbreak

    • Health care workers caring for those infected with monkeypox

    • Patients in whom no contraindication exists (ie, immunosuppression, eczema or other dermatitis in the vaccinee or household contacts, allergy to any component of the vaccine, and pregnancy or breastfeeding)