The progression of smallpox symptoms followed a severe and predictable course, typically unfolding over 2-3 weeks. It began with the invasion stage: a sudden high fever, severe headache, and body aches that often left patients bedridden. After 2-3 days, the early rash stage emerged as small red spots in the mouth and throat, making swallowing painful. These spots developed into sores that released virus into the saliva. Within a day, the characteristic skin rash appeared, starting on the face and spreading to the extremities in a "centrifugal" pattern. Over the next week, these lesions progressed through raised bumps → fluid-filled vesicles → pus-filled pustules, during which patients remained highly contagious. The pustular stage was particularly agonizing, as the skin felt like it was covered in hot coals, and the simultaneous development of all lesions created unbearable discomfort. Finally, in the scabbing stage, pustules crusted over and eventually fell off, leaving deep pitted scars, particularly on the face. This progression didn't just cause physical suffering; it isolated patients for weeks, threatened blindness if lesions affected the eyes, and left survivors with permanent visible scarring that often led to social stigma and economic hardship.