The smallpox virus is a highly contagious virus that causes the disease known as smallpox. It belongs to the Orthopoxvirus genus and is characterized by fever, body aches, and a distinctive rash that develops into fluid-filled blisters. Smallpox was responsible for significant mortality throughout history until its eradication in 1980. Vaccination against smallpox was crucial in controlling the virus. The smallpox vaccine, developed from the related cowpox virus, provided immunity and ultimately led to the global eradication of the disease. Today, smallpox remains the only human disease to have been completely eliminated through vaccination efforts.