The Worst Epidemics and Pandemics in History

Spreading along the Eastern Front during WWI, the Russian typhus epidemic infected over 30 million people. Typhus is caused by Rickettsia prowazekii bacteria, which spread to humans through infected body lice. Symptoms include headache, fever, abdominal pain, a full-body rash, and delirium caused by swelling of the membranes around the brain.

This new flu strain, H2N2, was a combination of avian and human flu viruses. Its mortality rate was partly due to its ability to cause pneumonia in an infected person even without a secondary bacterial infection. It emerged in China and spread throughout Asia to Europe and eventually to the rest of the world.

Various strains of the 1957 H2N2 virus recombined into a new H3N2 virus, causing the 1968 flu pandemic. The first case was reported in Hong Kong, where the disease spread quickly over the next few weeks. Multiple waves of the virus struck Europe, Australia, and Japan, with the second wave even deadlier than the first.

First reported in California in 1981, AIDS is now one of the largest pandemics in the world. HIV, the virus that causes AIDS, jumped from chimpanzees to humans in early 20th century Africa, and spreads through contact with bodily fluids. Although AIDS has killed at least 35 million people globally, current antiretroviral therapies can prevent its proliferation.

The ongoing COVID-19 pandemic, which has infected more than 762 million people worldwide, is the worst global pandemic of the last 100 years. Since the initial case in late 2019, there have been several waves of infection and near-global travel restrictions and lockdowns. Currently, 13.3 billion doses of vaccine have been administered to people around the world and about 69.9% of the world population has received at least one dose.