Europeans brought deadly viruses and bacteria, such as smallpox, measles, typhus, and cholera, for which Native Americans had no immunity (Denevan, 1976).

In terms of death tolls, smallpox killed the greatest number of Indians, followed by measles, influenza, and bubonic plague. Smallpox: The most deadly European disease was smallpox, a disease almost unknown in today’s world but common prior to the twentieth century.

Transmitted via coughing, sneezing and tactile infection, they wreaked devastation throughout Eurasian history – and in the era before antibiotics, thousands died. But not everyone. Smallpox is believed to have arrived in the Americas in 1520 on a Spanish ship sailing from Cuba, carried by an infected African slave.

Last Cases of Smallpox In late 1975, three-year-old Rahima Banu from Bangladesh was the last person in the world to have naturally acquired variola major.

At the time, there were no effective drugs or vaccines to treat this killer flu strain. Citizens were ordered to wear masks, schools, theaters and businesses were shuttered and bodies piled up in makeshift morgues before the virus ended its deadly global march.

The Spanish flu, also known as the 1918 influenza pandemic, was an unusually deadly influenza pandemic caused by the H1N1 influenza A virus. Lasting from February 1918 to April 1920, it infected 500 million people – about a third of the world’s population at the time – in four successive waves.

Since the whole world had been exposed to the virus, and had therefore developed natural immunity against it, the 1918 strain began to mutate and evolve in a process called “antigenic drift.” Slightly altered versions of the 1918 flu reemerged in the winters of 1919-1920 and 1920-1921, but they were far less deadly and …

More than 50 million people died of the disease, with 675,000 in the U.S. There is some disagreement on that figure, with recent researchers suggesting it was about 17.4 million deaths, while others go as high as 100 million. Generally speaking, the fatality rate for the Spanish flu is calculated at about 2%.

The definition from the U.S. Centers for Disease Control and Prevention is nearly the same: “A pandemic is a global outbreak of disease. Pandemics happen when a new virus emerges to infect people and can spread between people sustainably.” The Facebook post suggests that pandemics only occur every 100 years.