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SMALLPOX
SMALLPOXโICD-10: B03
โข Smallpox is a viral infection unique to humans. The disease has been eradicated caused by a global immunization program, with the last case having been reported in 1977. https://www.cdc.gov/smallpox/index.html https://www.who.int/health-topics/smallpox
โข Etiology. Variola major and Variola minor. Humans are only host. DNA virus replicates in cell cytoplasma. Transmitted by respiratory droplets. Variola major has a 30% to 50% mortality.
โข Pathogenesis. Enters respiratory tract, passing rapidly into local lymph nodes, and producing viremia. Infection with smallpox confers lifelong immunity.
โข Clinical manifestation. Acute onset of fever, followed by exanthem. Small red macules evolve to papules over 1 to 2 days. Initially, on the face, forearms and mouth, then gradually becomes disseminated. In 1 to 2 more days, papules become vesicles. Vesicles evolve to pustules about 4 to 7 days after onset of the rash (Fig. 27-8), and lasts for 5 to 8 days. Followed by umbilication and crusting (Fig. 27-8). Lesions are generally all at the same stage of development. Pockmarks/pitted scars occur in 65% to 85% of severe cases, especially on the face (Fig. 27-9). Secondary Staphylococcus aureus infection with abscesses and cellulitis may occur in smallpox lesions. Enanthema (tongue, mouth, or oropharynx) precedes exanthem by a day.
โข Differential Diagnosis. Severe chicken pox (varicella lesions are in different stages of development), measles, secondary syphilis (great pox), hand-foot-and-mouth disease (HFMD) (coxsackievirus A-16), cowpox, monkeypox, and tanapox.
โข Treatment. Report possible smallpox to public health officials; diagnosis confirmed in a Biological Safety Level 4 laboratory where staff members have been vaccinated. Cidofovir may be effective.
FIGURE 27-8 โข Smallpox: variola majorโMultiple pustules becoming confluent on the face.
FIGURE 27-9 โข Smallpox: scarring on faceโA 50-yearold Indian man with a history of smallpox as a child has multiple depressed scars on face 40 years after smallpox infection. (Used with permission from Atul Taneja, MD.)