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  • 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

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