Table 11.

Clinical presentations of smallpox

Syndrome	Proportion of Cases (%)	Clinical Features	Vaccination Status
Classic	90	Incubation period 10–14 d Febrile prodrome 1–4 d before rash, with constitutional symptoms (headache, myalgia, chills, abdominal pain, nausea, and vomiting) Enanthema of tongue, mouth, oropharynx followed by centrifugal rash starting with small macules, which become papules by day 4–7 and subsequently umbilicated vesicles	Unvaccinated
Modified	25 vaccinated 2 unvaccinated	Similar to classic but more rapid onset of rash and smaller lesions	Vaccinated or unvaccinated
Flat	7 unvaccinated	Prodrome with fever, confluent flat lesions develop and the patient seems very toxic, the skin subsequently sloughs off	Vaccinated or unvaccinated
Hemorrhagic	2	Shorter more severe prodrome with prostration, diffuse hemorrhagic lesions on the skin and mucous membranes, which eventually slough Pulmonary edema Pulmonary hemorrhage	Unvaccinated
Variola sine eruptione		Fever No rash	Vaccinated only

Data from Karwa M, Currie B, Kvetan V. Bioterrorism: preparing for the impossible or the improbable. Crit Care Med 2005;33(Suppl):S75–95; and Moore ZS, Seward JF, Lane JM. Smallpox. Lancet 2006;367(9508):425–35.