infectious diseases
Smallpox
Symptoms and Signs of Smallpox
Variola major has a 10- to 12-day incubation period (range 7 to 17 days), followed by a 2- to 3-day prodrome of fever, headache, backache, and extreme malaise. Sometimes severe abdominal pain and vomiting occur. After the prodrome, maculopapular lesions develop on the oropharyngeal mucosa, face, and arms, spreading shortly thereafter to the trunk and legs. The oropharyngeal lesions quickly ulcerate. After 1 or 2 days, the cutaneous lesions become vesicular, then pustular. Pustules are denser on the face and extremities than on the trunk, and they may appear on the palms. The pustules are round and tense and appear deeply embedded. Skin lesions of smallpox, unlike those of chickenpox, are all at the same stage of development on a given body part. After 8 or 9 days, the pustules become crusted. Severe residual scarring is typical. Case fatality rate is about 30%. Death results from a massive inflammatory response causing shock and multiple organ failure and usually occurs during the 2nd week of illness. About 5 to 10% of people with variola major develop either a hemorrhagic or a malignant (flat) variant. Thehemorrhagic formis rarer and has a shorter, more intense prodrome, followed by generalized erythema and cutaneous and mucosal hemorrhage. It is uniformly fatal within 5 or 6 days. Themalignant formhas a similar, severe prodrome, followed by development of confluent, flat, nonpustular skin lesions. In survivors, the epidermis frequently desquamates. Variola minor results in symptoms that are similar but much less severe, with a less extensive rash. Case fatality rate is<1%. 