Footnote
a The plague took several forms, including bubonic plague and pneumonic plague. Fleas, carried mainly by rats, spread the bubonic form, and droplets sprayed from infected persons most often spread the pneumonic form.
a The plague took several forms, including bubonic plague and pneumonic plague. Fleas, carried mainly by rats, spread the bubonic form, and droplets sprayed from infected persons most often spread the pneumonic form.