1, diagnosis According to the morphology, distribution and development process of smallpox rash and other characteristics, combined with the epidemiological situation, the diagnosis of typical cases is not difficult. Confirmation of the diagnosis of difficult cases depends on the examination of the virus and serum immunology. (1) Epidemiology: a history of pox should be asked, asking whether they have been to the epidemic area 2 weeks before the onset of the disease, whether there are similar cases around and whether there is a history of exposure to smallpox virus kept in the laboratory. (2) Clinical manifestations: characteristics of each stage, prodromal symptoms. Rash site and sequence, nature, transformation and fading characteristics, septicemia, body temperature in a cumulative peak curve, etc. (3) Laboratory tests: electron microscopy found smallpox virus particles, chick embryo chorionic vesicle inoculation, cell culture can be seen in the typical growth of smallpox virus, the discovery of inclusion bodies and the abundance of serological antibodies inventory, all help to confirm the diagnosis of smallpox. 2, differential diagnosis Typical smallpox in the prodromal phase should be distinguished from influenza, leptospirosis, sepsis, etc.. The rash period should be distinguished from measles, rubella, drug rash, scarlet fever, impetigo and chickenpox. Early hemorrhagic smallpox blood and hemorrhagic disease to distinguish. The current worldwide smallpox eradication, should be distinguished from monkeypox.