Poxviridae are double stranded DNA viruses with complex capsids and envelope. Poxviridae are the largest and most complex of all viruses. They are the largest of viruses- 300nm in diameter,visible with just a light microscope. Poxviridae infect a wide range of hosts. Many infect mammals like mice, camels, elephants, cattle, and monkey. (Chickenpox is not not cause by poxviridae) All poxviridae produce lesion and result in scars. Lesion progress through a series of stages. The lesion begin as flat, reddened macules, which then become a raised sores called papules. This papules will later be filled with a clear liquid, at this stage it will be called vesicles which then progress to pus-filled pustules, which is known as pocks or pox. Poxvirus pustules then dry up to form a crust, and because these lesions penetrate the dermis of the skin, they result in characteristic scars. Infection of poxviridae occurs primarily through inhalation of viruses in droplets or dried crust. Poxviridae remain stable for hours in air. The main poxvirus disease of human is smallpox-also known as variola.

Smallpox is the first human disease to be globally eradicated in nature. It played an important role in the history of microbiology, immunization and medicine. During the middle ages, 80% of the European poplulation contracted smallpox. It was later spread to Native Americans and resulted as many as 3.5 million people death. Variola exists in two forms or strains. Variola major causes severe disease with mortality rate of 20% or higher, depending on the age and general health of the host; and variola minor causes a less severe disease with mortality rate less than 1%. Both type of variola infect internal organs and produce fever, malaise, delirium and prostration before moving via the bloodstream to the skin where they produce recognizable pox. Both strians also leave severe scars on the skin of survivors, especially on the face.


At this period of time, Vaccination make it appearance. Edward Jenner realise that milkmaids are not infected with smallpox after they are infected with cowpox virus(Vaccinia). He vaccinate cowpox from milkmaids into an 8 years old boy (James Phipps). After the boy recover from cowpox he vaccinate him with smallpox and the boy did not contract smallpox. He carried many other successful test, and he name this idea vaccination from the word vaccinia, latin of cowpox. He was successful cause the antigens from cowpox virus are chemically similar to those of smallpox virus. The exposure of cowpox allowed the immunological memory in our body to be subsequent resistances against smallpox and cowpox virus and successful eradicated.

Signing off

Jiani