One of the reasons the Plague was so deadly is that it had such a short incubation period -- and was extremely contagious. If one contracted the infection from a flea bite, it took two to six days to incubate and for symptoms to begin. If it was spread by bacteria in the air, the incubation period was a mere one to three days. For most people, contact with someone who had the Plague could lead to their own infection and death within the week.

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