Monkeypox Clinical Presentation

  • Author: Mary Beth Graham, MD; Chief Editor: William D James, MD   more...
 
Updated: May 8, 2012
 

History

Monkeypox can cause a syndrome clinically similar to smallpox but overall is less infectious and less deadly.

Transmission can occur from contact with ill animals or animal reservoirs from Western Africa (eg, prairie dogs, rabbits, rats, mice, squirrels, dormice, monkeys, porcupines, gazelles). Additionally, preparing or ingesting infected animals can transmit monkeypox infection. Finally, direct cutaneous (skin-to-skin) or respiratory contact with an animal or person who is infected can transmit the infection.

The incubation period averages 12 days, ranging from 4-20 days.

In the prodrome or preeruptive stage (lasts 1-10 d), fever is commonly the first symptom (usually 38.5-40.5°C). The febrile illness is often accompanied by chills, drenching sweats, severe headache, backache, myalgia, malaise, anorexia, prostration, pharyngitis, shortness of breath, and cough (with or without sputum). Lymphadenopathy appears within 2-3 days after the fever. In the 2003 outbreak, 47% of patients had nodes measuring several centimeters in diameter in the cervical and submental areas.

In the exanthem (eruptive) stage, most persons develop a rash within 1-10 days after the onset of fever. The rash often starts on the face and then spreads to the rest of the body. It persists for 2-4 weeks until all lesions have shed the crusts. Encephalitis with immunoglobulin M found in the cerebrospinal fluid has been reported.[17]

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Physical

The most reliable clinical sign differentiating monkeypox from smallpox and chickenpox is enlarged lymph nodes, especially the submental, submandibular, cervical, and inguinal nodes. Note the image below.

Lymphadenopathy in monkeypox. Large nodes in the mLymphadenopathy in monkeypox. Large nodes in the mandibular, cervical, or inguinal region are commonly seen in monkeypox. The presence of significant lymphadenopathy helps differentiate monkeypox from smallpox and chickenpox.

With regard to enanthema, nonspecific lesions and inflammation of the pharyngeal, conjunctival, and genital mucosae have been observed.

In the exanthema stage, within a particular body region, lesions evolve synchronously over 14-21 days, similar to the development of lesions with smallpox. However, unlike smallpox, skin lesions may appear in crops. In contrast to smallpox, the lesions do not have a strong centrifugal distribution. Lesions progress from macules to papules to vesicles and pustules; umbilication, crusting, and desquamation follow. Most lesions are 3-15 mm in diameter.

Note the image below.

Umbilicated papule on the lower part of the leg. TUmbilicated papule on the lower part of the leg. This smaller lesion still shows the typical umbilicated morphology.

The face, the trunk, the extremities, and the scalp are involved. Lesions appear in covered and uncovered areas. Lesions may be seen on the palms and the soles. Necrosis, petechiae, and ulceration may be features. Pain is unusual, and, if it occurs, it is often associated with secondary bacterial infection. Pruritus may occur.

In patients who have been previously vaccinated against smallpox, a milder form of disease occurs. In children, the lesions may appear as nonspecific, erythematous papules that are 1-5 mm in diameter and suggestive of arthropod bite reactions. Subtle umbilication may be seen.

In the African outbreaks, 20% of unvaccinated patients developed a confluent, erythematous eruption on the face and the upper part of the trunk, which some authors have termed the septicemic rash of monkeypox.[16]

Hemorrhagic and flat forms, which can be seen with smallpox, have not been reported in patients with monkeypox. Deep pock scars can result as the lesions resolve.

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Causes

Outbreaks in western and central Africa have been linked to exposure to rats, rabbits, squirrels, monkeys, porcupines, and gazelles. Inhabitants of remote tropical rain forests may become infected from direct contact while capturing, slaughtering, and/or preparing these animals for food; ingestion has also been linked to infection. Because of the diversity of animals eaten by local inhabitants, conclusions about the relative risk of meat sources are not known with certainty.

In the DRC in 1997, animals caught from the wild were tested for the monkeypox virus. The following animals were found to have neutralizing antibodies against the monkeypox virus, suggesting a role as natural reservoirs: domestic pig (Sus scrofa), Gambian rat (Cricetomys emini), elephant shrew (Petrodromus tetradactylus), Thomas's tree/rope squirrel (Funisciurus anerythrus), Kuhl's tree squirrel (Funisciurus congicus), and sun squirrel (Heliosciurus rufobrachium).[4]

Human-to-human transmission supplanted the prominence of animal-to-human transmission in the 1996-1997 outbreak in the DRC. Crowded living quarters, poor hygiene, discontinuation of the smallpox vaccination, and decreased herd immunity were implicated. Respiratory droplets and direct contact with mucocutaneous lesions or fomites have been postulated as routes of human-to-human transmission.

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Contributor Information and Disclosures
Author

Mary Beth Graham, MD  Associate Professor, Department of Medicine, Division of Infectious Diseases, Medical College of Wisconsin

Mary Beth Graham, MD is a member of the following medical societies: American College of Physicians, Infectious Diseases Society of America, and Society for Healthcare Epidemiology of America

Disclosure: Nothing to disclose.

Coauthor(s)

Juliet L Gunkel, MD  Assistant Professor, University of Wisconsin School of Medicine and Public Health; Consulting Physician, University of Wisconsin Hospital

Juliet L Gunkel, MD is a member of the following medical societies: American Academy of Dermatology, American College of Mohs Micrographic Surgery and Cutaneous Oncology, American Medical Association, American Society for Dermatologic Surgery, Wisconsin Medical Society, and Women's Dermatologic Society

Disclosure: Nothing to disclose.

Janet Fairley, MD  Professor and Head, Department of Dermatology, University of Iowa, Roy J and Lucille A Carver College of Medicine

Janet Fairley, MD is a member of the following medical societies: American Academy of Dermatology, American Dermatological Association, American Federation for Medical Research, and Society for Investigative Dermatology

Disclosure: Nothing to disclose.

Specialty Editor Board

Julie R Kenner, MD, PhD  Consultant, Clinical Research, Medical Affairs, VaxGen, Inc; Private Practice, Kenner Dermatology Center

Julie R Kenner, MD, PhD is a member of the following medical societies: American Academy of Dermatology and American Society of Tropical Medicine and Hygiene

Disclosure: Nothing to disclose.

David F Butler, MD  Professor of Dermatology, Texas A&M University College of Medicine; Chair, Department of Dermatology, Director, Dermatology Residency Training Program, Scott and White Clinic, Northside Clinic

David F Butler, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American Medical Association, American Society for Dermatologic Surgery, American Society for MOHS Surgery, Association of Military Dermatologists, and Phi Beta Kappa

Disclosure: Nothing to disclose.

Jeffrey P Callen, MD  Professor of Medicine (Dermatology), Chief, Division of Dermatology, University of Louisville School of Medicine

Jeffrey P Callen, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American College of Physicians, and American College of Rheumatology

Disclosure: Amgen Honoraria Consulting; Celgene Honoraria Safety Monitoring Committee

Catherine M Quirk, MD  Clinical Assistant Professor, Department of Dermatology, University of Pennsylvania

Catherine M Quirk, MD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Dermatology

Disclosure: Nothing to disclose.

Chief Editor

William D James, MD  Paul R Gross Professor of Dermatology, Vice-Chairman, Residency Program Director, Department of Dermatology, University of Pennsylvania School of Medicine

William D James, MD is a member of the following medical societies: American Academy of Dermatology and Society for Investigative Dermatology

Disclosure: Elsevier Royalty Other

Additional Contributors

The authors and editors of eMedicine gratefully acknowledge the contributions of previous authors, Michael W. Peterson, DO, and Juliet L. Gunkel, MD, to the development and writing of this article.

References

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Vesicular rash on the dorsal aspect of the hand. Vesicopustules are seen; some have a central umbilication.
Umbilicated papule on the lower part of the leg. This smaller lesion still shows the typical umbilicated morphology.
Lymphadenopathy in monkeypox. Large nodes in the mandibular, cervical, or inguinal region are commonly seen in monkeypox. The presence of significant lymphadenopathy helps differentiate monkeypox from smallpox and chickenpox.
 
 
 
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