Week 3: Pathophysiology

The pathogenesis of human monkeypox is very similar to that of smallpox, with the exception that viral entry from a wildlife source probably occurs via small lesions on the skin or oral mucous membranes. Viral entry may also occur via the respiratory tract in the rare cases of person-to-person transmission.

Like smallpox, monkeypox virus replicates in lymphoid tissue, although it has a greater degree of lymphadenopathy. The virus first localizes in mononuclear phagocytic cells, is released into the bloodstream, and then localizes again in skin cells. For more detailed information, please refer to the pathogenesis section of smallpox virus.

Monkeypox Transmission Cycle in Central Africa

 Monkeypox is caused by an Orthopoxvirus named monkeypox. The viruses are oval brick-shaped viruses that have a lipoprotein layer with tubules or filaments that cover the viral DNA. It is a zoonotic virus with primary transmission believed to occur through direct contact with infected animals or possibly by ingestion of their inadequately cooked flesh. Inoculation may be from cutaneous or mucosal lesions on the animal, especially when the skin barrier is compromised secondary to bites, scratches, or other trauma.  

 

UCLA infectious disease expert Anne Rimoin talks about the alarming recent rise in monkeypox in the Democratic Republic of the Congo

The majority of the clinical characteristics of human monkeypox infection mirror those of smallpox. An initial febrile prodrome is accompanied by generalized headache and fatigue. Prior to, and concomitant with, rash development is the presence of maxillary, cervical, or inguinal lymphadenopathy (1–4 cm in diameter) in many patients (Figure 1). Enlarged lymph nodes are firm, tender, and sometimes painful. Lymphadenopathy was not characteristic of smallpox.

Cervical lymphadenopathy in a patient with active monkeypox during a monkeypox outbreak in Zaire, 1996–1997. 

A patient with monkeypox showing characteristic lesions.

References:
Davis, C. (2014, April 30). Monkeypox Symptoms, Causes, Treatment - What causes monkeypox? How is monkeypox transmitted? - MedicineNet. Retrieved April 13, 2015, from http://www.medicinenet.com/monkeypox/page3.htm#what_causes_monkeypox_how_is_monkeypox_transmitted
McCollum, A. (2013, October 24). Clinical Infectious Diseases. Retrieved April 13, 2015, from http://cid.oxfordjournals.org/content/early/2013/11/10/cid.cit703.full