Monkeypox Outbreak — Nine States, May 2022

Faisal S. Minhaj, PharmD; Yasmin P. Ogale, PhD; Florence Whitehill, DVM; Jordan Schultz, MPH; Mary Foote, MD; Whitni Davidson, MPH; Christine M. Hughes, MPH; Kimberly Wilkins; Laura Bachmann, MD; Ryan Chatelain, MPH; Marisa A.P. Donnelly, PhD; Rafael Mendoza, MPH; Barbara L. Downes, MS; Mellisa Roskosky, PhD; Meghan Barnes, MSPH; Glen R. Gallagher, PhD; Nesli Basgoz, MD; Victoria Ruiz, PhD; Nang Thu Thu Kyaw, PhD; Amanda Feldpausch, DVM; Amy Valderrama, PhD; Francisco Alvarado-Ramy, MD; Chad H. Dowell, MS; Catherine C. Chow, MD; Yu Li, PhD; Laura Quilter, MD; John Brooks, MD; Demetre C. Daskalakis, MD; R. Paul McClung, MD; Brett W. Petersen, MD; Inger Damon, MD, PhD; Christina Hutson, PhD; Jennifer McQuiston, DVM; Agam K. Rao, MD; Ermias Belay, MD; Andrea M. McCollum, PhD


Morbidity and Mortality Weekly Report. 2022;71(23):764-769. 

In This Article

Abstract and Introduction


On May 17, 2022, the Massachusetts Department of Public Health (MDPH) Laboratory Response Network (LRN) laboratory confirmed the presence of orthopoxvirus DNA via real-time polymerase chain reaction (PCR) from lesion swabs obtained from a Massachusetts resident. Orthopoxviruses include Monkeypox virus, the causative agent of monkeypox. Subsequent real-time PCR testing at CDC on May 18 confirmed that the patient was infected with the West African clade of Monkeypox virus. Since then, confirmed cases* have been reported by nine states. In addition, 28 countries and territories, none of which has endemic monkeypox, have reported laboratory-confirmed cases. On May 17, CDC, in coordination with state and local jurisdictions, initiated an emergency response to identify, monitor, and investigate additional monkeypox cases in the United States. This response has included releasing a Health Alert Network (HAN) Health Advisory, developing interim public health and clinical recommendations, releasing guidance for LRN testing, hosting clinician and public health partner outreach calls, disseminating health communication messages to the public, developing protocols for use and release of medical countermeasures, and facilitating delivery of vaccine postexposure prophylaxis (PEP) and antivirals that have been stockpiled by the U.S. government for preparedness and response purposes. On May 19, a call center was established to provide guidance to states for the evaluation of possible cases of monkeypox, including recommendations for clinical diagnosis and orthopoxvirus testing. The call center also gathers information about possible cases to identify interjurisdictional linkages. As of May 31, this investigation has identified 17§ cases in the United States; most cases (16) were diagnosed in persons who identify as gay, bisexual, or men who have sex with men (MSM). Ongoing investigation suggests person-to-person community transmission, and CDC urges health departments, clinicians, and the public to remain vigilant, institute appropriate infection prevention and control measures, and notify public health authorities of suspected cases to reduce disease spread. Public health authorities are identifying cases and conducting investigations to determine possible sources and prevent further spread. This activity was reviewed by CDC and conducted consistent with applicable federal law and CDC policy.

Monkeypox, a zoonotic disease for which the animal reservoir is unknown,[1] is endemic in several Central and West African countries. There are two clades of Monkeypox virus, West African, and Congo Basin, the latter causing more severe illness.[1,2] The last United States monkeypox outbreak was secondary to imported small mammals from Ghana in 2003**; however, since monkeypox reemerged in Nigeria in 2017, isolated cases outside Africa have been reported either among persons with recent travel to Nigeria or among secondary contacts of persons with travel-associated cases.[2,3] Patients with monkeypox typically experience a febrile prodrome 5–13 days after exposure (range = 4–17 days), which often includes lymphadenopathy, malaise, headache, and muscle aches; this prodrome might depend on the nature of exposure.[4] The prodrome is followed 1–4 days later by the onset of a characteristic deep-seated, vesicular or pustular skin rash with a centrifugal distribution (Figure); the lesions are well circumscribed and often umbilicate or become confluent, progressing over time to scabs. The rash can be disseminated. Some recent cases have begun atypically, with lesions in the genital and perianal region and without subjective fever or other prodromal symptoms. For this reason, cases might be confused with more commonly seen infections such as varicella zoster or sexually transmitted infections (STIs) (e.g., genital herpes or syphilis). The case-fatality ratio for the West African clade of monkeypox is reported to be 1% and might be higher in immunocompromised persons.[1,5,6]


Characteristic monkeypox lesions*,† — United States, May 2022
*The rash associated with monkeypox involves firm, deep-seated, and well-circumscribed vesicles or pustules, which might umbilicate or become confluent. Lesions progress over time to scabs.
Photos used with patients' permission.

A person is considered infectious from the onset of illness until all lesions have crusted over, those crusts have separated, and a fresh layer of healthy skin has formed under the crust. Human-to-human transmission occurs by direct contact with infected body fluids or lesions, via infectious fomites, or through respiratory secretions, that typically require prolonged interaction.[1] Historically, documented reports of human-to-human transmission have been among household contacts and shared housing inhabitants (e.g., in prisons), and health care providers who have had close, sustained contact with a patient or patient fomites (e.g., bedding).[6,7]

*Confirmed case for this outbreak is defined as either a positive orthopoxvirus assays or Monkeypox virus assays. Case counts as of May 31, 2022 at 11:59 p.m. EDT.
Argentina, Australia, Austria, Belgium, Canada, Czech Republic, Denmark, Finland, France, Germany, Gibraltar, Hungary, Ireland, Israel, Italy, Malta, Mexico, Morocco, Netherlands, Norway, Portugal, Slovenia, Spain, Sweden, Switzerland, United Arab Emirates, United Kingdom, and United States.
§One case in Florida was initially identified in another country and is not included in this report.
45 C.F.R. part 46, 21 C.F.R. part 56; 42 U.S.C. Sect. 241(d); 5 U.S.C. Sect. 552a; 44 U.S.C. Sect. 3501 et seq.