Plague — 1720-1722

Plague, an infectious fever caused by a bacterium transmitted from rodents to humans by the bite of infected fleas, caused some of the worst pandemics in history, according to Britannica.com.

Cholera — 1817

The first pandemic of cholera “Since first spreading from Calcutta along the Ganges Delta in 1817, it has killed millions,” says the Robert Wood Johnson Foundation, which supports health research and programs.

Spanish flu — 1918-1919

This influenza pandemic is more accurately called “The Great Influenza” by modern historians.

The pandemic “was caused by an H1N1 virus with genes of avian origin. Although there is not universal consensus regarding where the virus originated, it spread worldwide during 1918-1919,” according to the CDC. “In the United States, it was first identified in military personnel in spring 1918. It is estimated that about 500 million people or one-third of the world’s population became infected with this virus. The number of deaths was estimated to be at least 50 million worldwide with about 675,000 occurring in the United States.”

Coronavirus — 2019-2020

COVID-19 can be traced back at least to Dec. 31, 2019, when the government in Wuhan, China, confirmed that health authorities were treating dozens of cases of pneumonia from an unknown cause. Eight days later, China identified a new type of coronavirus. The first coronavirus case in the United States was confirmed on Jan. 21, 2020.

The World Health Organization declared COVID-19 a pandemic on March 11, 2020, saying it is the first pandemic caused by a coronavirus.