Hemorrhages in the mucous membranes appear to occur less often than in the early hemorrhagic form. Sometimes the rash forms pustules which bleed at the base and then undergo the same process as in ordinary smallpox. This form of the disease is characterized by a decrease in all of the elements of the coagulation cascade and an increase in circulating antithrombin. This form of smallpox occurs anywhere from three to 25 percent of fatal cases, depending on the virulence of the smallpox strain. Most people with the late-stage form die within eight to 10 days of illness. Among the few who recover, the hemorrhagic lesions gradually disappear after a long period of convalescence. The case fatality rate for late hemorrhagic smallpox is around 90-95%. Pregnant women are slightly more likely to experience this form of the disease, though not as much as early hemorrhagic smallpox. Cause
Smallpox was caused by infection with Variola virus, which belongs to the family Poxviridae, subfamily Chordopoxvirinae, and genus Orthopoxvirus. Evolution
The date of the appearance of smallpox is not settled. It most probably evolved from a terrestrial African rodent virus between 68,000 and 16,000 years ago. The wide range of dates is due to the different records used to calibrate the molecular clock. One clade was the Variola major strains (the more clinically severe form of smallpox) which spread from Asia between 400 and 1,600 years ago.
For example, several relatives of Henry VIII of England survived the disease but were scarred by it. These include his sister Margaret, his wife Anne of Cleves, and his two daughters: Mary I in 1527 and Elizabeth I in 1562. Elizabeth tried to disguise the pockmarks with heavy makeup. Mary, Queen of Scots, contracted the disease as a child but had no visible scarring. In Europe, deaths from smallpox often changed dynastic succession. Louis XV of France succeeded his great-grandfather Louis XIV through a series of deaths of smallpox or measles among those higher in the succession line. He himself died of the disease in 1774. Peter II of Russia died of the disease at 14 years of age. Also, before becoming emperor, Peter III of Russia caught the virus and suffered greatly from it. He was left scarred and disfigured. His wife, Catherine the Great, was spared but fear of the virus clearly had its effects on her. She feared for the safety of her son, Paul, so much that she made sure that large crowds were kept at bay and sought to isolate him. Eventually, she decided to have herself inoculated by a British doctor, Thomas Dimsdale. While this was considered a controversial method at the time, she succeeded. Paul was later inoculated as well.