smallpox

Smallpox is a contagious disease caused by the Variola virus. It was historically a major cause of illness and death worldwide, but global vaccination campaigns led by the World Health Organization eradicated the disease in 1980. Today there are no naturally occurring cases; variola virus stocks are kept only in secure laboratories for research and emergency preparedness.

Transmission occurs primarily through prolonged face-to-face contact and inhalation of respiratory droplets during the prodromal phase, but the virus can also spread via contaminated bedding and clothing. The incubation period is typically 7 to 17 days. Early symptoms include fever, malaise, headache, and backache, followed by a characteristic rash that begins on the face and spreads to the limbs. The rash progresses through stages—macules, papules, vesicles, pustules, and crusts—and the lesions are often in the same stage of development on most of the body. The illness can be severe and, in variola major, life-threatening; variola minor (alastrim) is milder.

Two main clinical forms exist. Variola major has higher mortality (historically around 30% or more, depending on the outbreak and access to care) and subtypes such as ordinary, modified, hemorrhagic. Variola minor is less virulent. There is no specific antiviral treatment for smallpox; management is supportive, though vaccination can provide protection and post-exposure vaccination can prevent disease if given promptly. Vaccination with vaccinia-based vaccines is effective and was central to eradication.

After eradication, routine vaccination ceased in most places, but vaccine stockpiles and surveillance systems remain for potential outbreak response. The disease’s disappearance is one of the major public health triumphs of modern medicine.