Diphtheria was a communicable disease that was prevalent until the early 20th century. A vaccine was developed from the inactivated diphtheria toxoid in 1921, and vaccinations were common from the 1940s onward. Clara Clayton contracted the disease in the year 1866, when she was eleven years old, and was under a quarantine for three months.
While she convalesced, her father bought her a telescope and put it next to her bed so she could see everything outside the window. Thereafter, she was interested in science and astronomy, qualities that she had in common with her future husband, Emmett Brown.
Diphtheria was an acute respiratory infection and the death rate from the disease was high, with chances of death being as high as 40 percent. The cause, a bacteria known as Corynebacterium diphtheriae, was not known in 1866. Diphtheria not only caused painful inflammations of the upper respiratory tract, it also posed the danger of asphyxiation from the clogging of the mucous membrane. The toxin could also damage the heart muscles and the nervous system. Although a vaccine can prevent, and antibiotics can treat, the infection, neither of those had were available when Clara became ill with the disease in 1866. Fortunately, her own immune system allowed the infection to clear up on its own, and after three months of bedrest, she was able to continue her education.
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