"In 1768, Dr. John Dagleish of Norfolk, Virginia set forth in the April 14 issue of the Virginia Gazette an essay on smallpox, explaining the different types and their characteristics:

1. Distinct: pustules few and far separated. When eruption is completed, no more ailing.
   
2. Coherent: pustules distinct, crowded onto the face. Sore throat and second fever occur. Some death in unfavorable times.
   
3. Confluent: pustules erupt small and close, running into each other, very bad dangerous second fever. Many deaths, a very frequent type.
   
4. Purple: no pustules, or very few, some purple spots appear; about the fourth day pain and anguish abate so much that the unskillful are deceived. All die, very rare type.

The first three types show how the immune system was able to cope well, badly and very badly to the virus, respectively. The last case shows it ot working at all. The pus mentioned here is white blood cells that died while trying to defeat the virus. When none at all are produced because of the ability to mount any defense at all it is for the lack of one raw material needed by the body. The purple dots are a symptom of scurvy.

The virus encodes for ascorbate. The less you have and get the worse you are off you are. In the case of purple smallpox you almost certainly die of scurvy long before you die of smallpox - there is so little an immune response can not even be mounted and the heart stops not long after, below a certain level of ascorbate the heart can not beat as ascorbate is used in the production of all energy in the body without exception in ATP synthesis in the mitochondria. The virus needs it to make more viruses, so it takes yours. Under the right conditions (severe malnutrition) it can take all of it in a matter of days, just as Ebola can. This is what makes disease virulent - the rate at which they take out of you the chemical you need to mount a proper immune response..

"The four stages of smallpox are:

1. Dormant: the period from first receiving the infection to the time the fever begins. The constitution of the patient has a lot to do with which type is contracted — this is established in the first fever.
   
2. Eruptive: from the beginning of the first fever until eruption is completed and pustules ripen. The worst time for the body to throw off the disease.
   
3. Turn of the pox: pustules dry and blacken, patient is extremely bad in appearance. Second fever comes. Most tragic events take place at this stage. Treatment is what is recommended by the physician.
   
4. Convalescent: patient is judged to be out of danger, though further care is still necessary. These pustules left pockmarks on the faces of those who had had the disease, though the prevalence of the disfigurement has been greatly exaggerated to coincide with that of Europe."

SMALLPOX IN THE 18th CENTURY
Susan Pryor, 1984
Research Report
Colonial Williamsburg Foundation - 0201