Journal Article

Clinical Characteristics of Human Monkeypox, and Risk Factors for Severe Disease

Gregory D. Huhn, Audrey M. Bauer, Krista Yorita, Mary Beth Graham, James Sejvar, Anna Likos, Inger K. Damon, Mary G. Reynolds and Matthew J. Kuehnert

in Clinical Infectious Diseases

Published on behalf of Infectious Diseases Society of America

Volume 41, issue 12, pages 1742-1751
Published in print December 2005 | ISSN: 1058-4838
Published online December 2005 | e-ISSN: 1537-6591 | DOI:
Clinical Characteristics of Human Monkeypox, and Risk Factors for Severe Disease

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Background. Human monkeypox is an emerging smallpox-like illness that was identified for the first time in the United States during an outbreak in 2003. Knowledge of the clinical manifestations of monkeypox in adults is limited, and clinical laboratory findings have been unknown.

Methods. Demographic information; medical history; smallpox vaccination status; signs, symptoms, and duration of illness, and laboratory results (hematologic and serum chemistry findings) were extracted from medical records of patients with a confirmed case of monkeypox in the United States. Two-way comparisons were conducted between pediatric and adult patients and between patients with and patients without previous smallpox vaccination. Bivariate and multivariate analyses of risk factors for severe disease (fever [temperature, ⩾38.3°C] and the presence of rash [⩾100 lesions]), activity and duration of hospitalization, and abnormal clinical laboratory findings were performed.

Results. Of 34 patients with a confirmed case of monkeypox, 5 (15%) were defined as severely ill, and 9 (26%) were hospitalized for >48 h; no patients died. Previous smallpox vaccination was not associated with disease severity or hospitalization. Pediatric patients (age, ⩽18 years) were more likely to be hospitalized in an intensive care unit. Nausea and/or vomiting and mouth sores were independently associated with a hospitalization duration of >48 h and with having ⩾3 laboratory tests with abnormal results.

Conclusion. Monkeypox can cause a severe clinical illness, with systemic signs and symptoms and abnormal clinical laboratory findings. In the appropriate epidemiologic context, monkeypox should be included in the differential diagnosis for patients with unusual vesiculopustular exanthems, mucosal lesions, gastrointestinal symptoms, and abnormal hematologic or hepatic laboratory findings. Clinicians evaluating a rash illness consistent with possible orthopoxvirus infection should alert public health officials and consider further evaluation.

Journal Article.  4298 words.  Illustrated.

Subjects: Infectious Diseases ; Immunology ; Public Health and Epidemiology ; Microbiology

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