A more fulminant form, hemorrhagic smallpox or blackpox, occurs in approximately 3 to 10% of cases. The incubation period is shorter, and the characteristic rash presents as a dark, dusky erythema followed by petechiae and frank hemorrhage into the skin and GI tract. This form is almost uniformly fatal [64] ; death occurs 5 to 6 days after the onset of the rash [62] . This illness could be confused with meningococcemia or acute leukemia.