Smallpox, also known as variola, is a viral disease caused by the variola virus, a double-stranded DNA virus belonging to the genus Orthopoxvirus. This virus initially infects the upper respiratory tract before spreading systemically through the bloodstream and lymphatic system, targeting vital organs such as the lungs and liver. One of the hallmark features of smallpox is its severe skin rash, characterized by fluid-filled vesicles that progress to pustules, often resulting in significant scarring. The skin lesions compromise the body's primary protective barrier, increasing vulnerability to secondary infections.
Historically, smallpox was one of the deadliest infectious diseases, responsible for an estimated 300 to 500 million deaths in the twentieth century alone. The disease had a high fatality rate of approximately 30% in unvaccinated individuals, which is substantially higher than many other viral infections like measles, whose fatality rates are typically below 1%. Transmission occurred mainly through close contact, primarily via inhalation of respiratory droplets expelled during coughing, sneezing, or talking, as well as through direct contact with contaminated materials or lesions. Although less contagious than measles, smallpox was far more lethal.
Symptoms of smallpox began with a high fever, fatigue, and malaise, followed by the appearance of the distinctive rash starting on the face, arms, and legs before spreading to the rest of the body. The progression of skin lesions from vesicles to pustules was a key diagnostic feature, helping to differentiate smallpox from other rash-causing diseases. Diagnosis historically relied on clinical observation of these characteristic lesions, but modern methods would include serological testing to detect antibodies or viral components.
Before eradication, there was no specific antiviral treatment for smallpox; medical care was supportive, focusing on symptom management and patient isolation to prevent further spread. The global eradication of smallpox in 1980 was achieved through widespread vaccination efforts, marking it as the first and only human disease to be completely eradicated. This monumental public health success underscores the critical role of vaccination in controlling and eliminating infectious diseases.
