Poxviruses are the largest animal viruses; they can cause disease of varying severity in humans.
Smallpox is the only poxvirus whose sole reservoir is humans, which allowed its eradication.
The virus used in smallpox vaccines, vaccinia, has its own adverse effects.
Monkeypox is a zoonotic infection endemic in Africa.
Milker’s nodule and orf mainly cause localized cutaneous infections.
Molluscum contagiosum is generally a benign cutaneous disease most frequently seen in children and immunocompromised individuals.
Histopathologic features of poxviral cutaneous lesions include the presence of intracytoplasmic eosinophilic inclusion bodies.
Poxviruses are a family of double-stranded DNA viruses that replicate in the cytoplasm of host cells (Table 166-1). They are the largest known animal viruses and can be seen with light microscopy.1 The poxvirus family is divided into multiple genera. Four genera affect humans: Orthopoxvirus, Parapoxvirus, Molluscipoxvirus, and Yatapoxvirus. The poxviruses that cause significant disease in humans are reviewed here. Their effects on humans range from systemic disease to localized infection to epithelial cell proliferation without other findings.
TABLE 166-1Poxviruses with Humans as Hosts ||Download (.pdf) TABLE 166-1 Poxviruses with Humans as Hosts
|GENUS ||SPECIES ||HOSTS ||MAIN PORTAL OF ENTRY ||CLINICAL FEATURES ||TREATMENT |
|Orthopoxvirus ||Variola virus (smallpox) ||Humans ||Respiratory tract || |
High fever and myalgia precede oropharyngeal enanthem and centrifugal exanthem.
Simultaneous progression of skin lesions from macules to papulovesicles, pustules, and crusts, resulting in significant scars.
Last reported case in 1978; concern for use in bioterrorism.
Postexposure vaccination to reduce severity and disease occurrence (prior to onset of clinical symptoms)
Tecovirimat (SIGA Technologies)
Brincidofovir (CMX001, Chimerix)
|Vaccinia virus ||Humans ||Skin || |
Used as vaccine for smallpox. Also protects against monkeypox.
Vaccination site progresses from papule to vesicle, pustule, and crust, leaving scar.
Adverse events occur when virus spreads locally or in a generalized manner, more severe in individuals with disruption of the skin barrier or immune compromise.
Symptomatic treatment for minor local reactions, or for typical systemic symptoms
Vaccinia immune globulin or cidofovir for extensive lesions distant from vaccination site
Fluid and electrolyte repletion
|Monkeypox virus ||Rodents, humans, monkeys, anteaters ||Skin ||Clinical presentation similar to that of smallpox but with more prominent lymphadenopathy and lower mortality. || |
Postexposure prophylaxis with vaccinia virus (4-14 days after exposure)
|Cowpox virus ||Rodents, cats, humans, cattle ||Skin || |
Contact with infected animal host gives rise to papule that becomes vesicular, hemorrhagic, pustular, and ulcerative; resulting eschar heals over 3-4 weeks with scarring.
Constitutional symptoms and lymphangitis common. Can be extensive or severe if skin barrier is disrupted.
|No known treatment |
|Parapoxvirus ||Orf virus ||Sheep, goats, humans ||Skin || |
Contact with infected animal or fomite leads to 1 or more papules, usually on hand.
Papule progresses into pustule or nodule with central umbilication and surrounding gray-white or violaceous ring and outer zone of erythema.
Becomes weepy, then dries and crusts.
Healing occurs over 4-8 weeks, ...