The causative agent of smallpox disease is the smallpox virus, which is a poxvirus and contains DNA in its core, and therefore is a DNA virus. Smallpox is a highly contagious infectious disease, and the disease is relatively serious, and the death rate is very high in the past when medical conditions were poor. The smallpox virus is mainly found in the body fluids of patients and can be spread through droplets in the air; some patients have secondary diseases of the urinary system and gastrointestinal tract, so the virus may also be carried in the urine and stool; at the same time, clothing contaminated with body fluids of patients can also spread smallpox virus; if a pregnant woman is sick, it can also be transmitted through the placenta. The most important clinical manifestation of the disease is the appearance of a large rash, which will leave a lifelong scar after ulceration, accompanied by high fever, chills, fainting, pneumonia and other systemic symptoms, eventually leading to death. China eradicated smallpox nationwide in 1961 by vaccinating against cowpox and other measures, and the World Health Organization declared the global eradication of smallpox in 1980 and stopped vaccinating against cowpox, and now the smallpox virus is only kept in a few key laboratories, so there is no need to worry about the occurrence of smallpox disease.