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Volume 13, Number 9—September 2007

Spectrum of Infection and Risk Factors for Human Monkeypox, United States, 2003

Mary G. Reynolds*Comments to Author , Whitni B. Davidson*, Aaron T. Curns*, Craig S. Conover†, Gregory Huhn*‡, Jeffrey P. Davis§, Mark Wegner§, Donita R. Croft§, Alexandra Newman*§, Nkolika N. Obiesie¶, Gail R. Hansen¶, Patrick L. Hays¶, Pamela Pontones#, Brad Beard#, Robert Teclaw#, James F. Howell#, Zachary Braden*, Robert C. Holman*, Kevin L. Karem*, and Inger K. Damon*
Author affiliations: *Centers for Disease Control and Prevention, Atlanta, Georgia, USA; †Illinois Department of Public Health, Chicago, Illinois, USA; ‡Rush University, Chicago, Illinois, USA; §Wisconsin Department of Health and Family Services, Madison, Wisconsin, USA; ¶Kansas Department of Health and Environment, Topeka, Kansas, USA; #Indiana State Department of Health, Indianapolis, Indiana, USA;

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Table 1

Criteria used to define categories of study participants, monkeypox virus outbreak, United States, 2003*

classification Classification by case definition† Criteria met
Epidemiologic‡ Clinical§ Laboratory¶
Case Confirmed Yes Yes Yes#
Probable Yes Yes (fever with vesicular pustular rash, or rash of unspecified type plus IgM) No (if rash type unspecified, IgM 7–56 d after rash onset)
Not included Suspect Yes No (fever or rash of unspecified type) No
Control** Not a case Yes No No
Infected but not diseased Unclassified Yes No No (IgM detected at time of study)

*IgM, immunoglobulin M.
†Available from, January 2004 (3,12,13).
‡Epidemiologic criteria for classification of monkeypox cases included exposure to an exotic or wild mammalian pet (obtained on or after the known importation event) exhibiting signs of illness (e.g., conjunctivitis, respiratory symptoms, and rash); exposure to an exotic or wild mammalian pet that had been exposed to an animal infected with monkeypox; or exposure to a suspected, probable, or confirmed human case of monkeypox.
§Clinical criteria were rash (macular, papular, vesicular, or pustular; generalized or localized; discrete or confluent) plus fever (subjective or measured temperature >99.3°F [>37.4°C]), plus >2 other signs and symptoms (chills and/or sweats, headache, backache, lymphadenopathy, sore throat, cough, shortness of breath), all beginning <21 d after last possible exposure.
¶Laboratory criteria included culture of monkeypox virus, or demonstration of monkeypox virus DNA by PCR from patient clinical specimens, or demonstration of virus morphologically consistent with an orthopoxvirus by electron microscopy or immunohistochemical testing methods (in the absence of exposure to another orthopoxvirus).
#Positive laboratory findings were sufficient to confirm a monkeypox case in the absence of complete clinical or epidemiologic history.
**Persons investigated but ruled out as having monkeypox virus infections were eligible to enroll in the study as controls; additional controls were identified as in Patients and Methods.

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