The Third Plague: 12 million (1855–1959)
While it never really went away, the bubonic plague resurged quite violently in 1855. It started in Yunnan, China, and rapidly spread over the port cities of Guangzhou and Hong Kong by 1894.
Outbound ships seeded burgeoning clusters in Bombay, Calcutta, Cape Town, and San Francisco by the turn of the century. However, it didn’t stop there: before 1959, 12 million people from all over the world, half of them living in India, died.
But science was catching up quite rapidly, meaning that this was the final pandemic of the bubonic plague. The causative bacteria that we mentioned above, Yersinia pestis, was identified in 1894 in Hong Kong.
The observation that a litter of dead rats in the streets preceded an outbreak ultimately convinced scientists that rat fleas were the carriers. Rat-proofing measures and insecticides helped for a while. The discovery of effective treatments would ultimately tame the most horrendous epidemic disease the world has ever known.
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