Smallpox was the silent killer, maleficent and effective once it attacked. By the time you realized it was already in your system, it was usually too late to do anything.
One or two days after the appearance of the characteristic rash, it will become a solid or cystic raised spot on the skin that is less than 1 centimetre wide. By the third or fourth day, the bumps will be filled with opalescent pus. This fluid became opaque and turbid within 24–48 hours, indicating the disease was progressing into another stage.
Sometimes, the blisters merged into sheets, forming a confluent rash, which began to detach the outer layers of skin from the underlying flesh. In that phase, less than half of the patients had the chance to survive.
