Throughout history, plague epidemics have erupted in several eras, below are the worst plagues that has ravaged mankind.

1. *Black Death:*
About a third of Europe’s population was wiped out in the 14th century by bubonic plague, also known as the Black death.
Black Death, which caused great destruction across Europe between 1347 and 1351, is estimated to have killed 75 million to 100 million people. 

*2.VHFs*
Similar to the disease caused by the Ebola or dengue viruses, viral hemorrhagic fevers (VHF) are contagious, continuous and for the most part, lethal. VHF outbreaks swept through Mexico between 1545 and 1548 and killed an estimated 5 million to 15 million of the native population, making it the worst disease epidemic in the country's history. This mysterious illness came to be known as "cocoliztli.

*3.Spanish flu:*
Spanish flu or influenza was caused by a deadly subtype of the H1N1 virus in 1918-1920. The Spanish influenza is considered the worst in modern history, killing an estimated 50 million to 100 million people in just 18 months. About 500 million people were estimated to be infected by the virus.

*4.Swine flu:*
Swine flu killed approximately 2 million people between 1957 and 1958, while 1 million people each died in the flu outbreaks in Russia and Hong Kong in the years 1889-1890 and 1968-1969, respectively. The swine flu pandemic of 2009 killed an estimated 284,500 people.

Extracted from: https://www.dailysabah.com/life/health/10-deadliest-infectious-disease-outbreaks