Smallpox manifestations and survival during the Boston epidemic of 1901 to 1903.

Clinical records of 243 patients with smallpox consecutively admitted to the Southampton Street smallpox hospital in Boston, Massachusetts, during the 1901-1903 epidemic were reviewed. Smallpox was divided into five categories of varying severity; 47% of patients had varioloid, a relatively mild form of the disease usually occurring in previously vaccinated individuals with incomplete immunity. Survival information is available for 206 patients, of whom 36 (17.5%) died. Vaccination status, disease severity, and age were associated with survival, whereas sex, birthplace, and race were not. While full recovery often took weeks, most deaths occurred 7 to 14 days after the onset of symptoms, and all deaths occurred within 18 days of symptom onset. Smallpox was eradicated worldwide in 1977, but knowledge of the disease is essential because its cause, variola virus, is considered a potential biological weapon.