Typhus fever is spread by lice. The war brought on poor sanitation that probably led to a higher density of lice and made the transmission more prevalent.

Typhus fever caused three million deaths in Russia alone.

This bubonic plague pandemic started in the Yunnan province in China. Over the next 20 years, rats carried the infectious fleas responsible for the disease to Hong Kong and port cities around the world.

It caused almost 10 million deaths.

Also known as the plague of Galen, this plague was possibly caused by smallpox or measles.

Almost 2 000 deaths per day were recorded in Rome. The total death toll was about 5 million.

It is believed that HIV originated in the Democratic Republic of the Congo around 1920 when the disease was spread from chimpanzees to humans.

The first cases of AIDs were reported in 1981, and since then, HIV has resulted in an estimated 65 million infections and 25 million deaths.

The Great Flu claimed between 20 million and 40 million lives. This disease killed more people than WW1.

The Asian Flu Pandemic was an outbreak of avian influenza that started in China and spread worldwide.

The estimated death rate was one to two million people.

This pandemic affected the Eastern Roman Empire, specifically Constantinople and port cities along the Mediterranean sea. Necrosis of the limbs was one of the terrifying symptoms.

An estimated 25 million people died. The plague returned in waves but was not as severe as this one.

The Great Plague started in China and spread all along trade routes to Constantinople and Europe.
An estimated 60% of the European population was wiped out.