List of 10 Deadliest Diseases in History

The progress of science and medicine after the 19th century has eradicated many diseases either via vaccination or development of effective treatments. Unfortunately, many of the deadliest diseases in history are still claiming thousands of lives, mostly in the developing countries. At the moment of writing, medicine still does not have a cure for viral diseases, while the industrialized countries are also facing a problem with antibiotic resistance as well as the risk of tropical illnesses spreading to temperate areas as a result of climate change.


One of the deadliest diseases in history was fortunately eradicated by 1980 as a result of worldwide vaccination campaign. It is impossible to tell how many people died from smallpox but only during the 20th century, the disease is estimated to claim from 300 to 500 million lives. But despite the fact that no new cases were reported since 1980, there are concerns that it could be used for biological warfare as the smallpox virus is still kept in laboratories in the United States and Russia.

Bubonic plague

The disease which was responsible for the so-called Black Death which reached its height between 1348 and 1350 killed about one third of the population in medieval Europe. It is caused by a bacterium called Yersinia pestis which is today successfully treated with antibiotics. Bubonic plague is extremely rare but occasional outbreaks still occur. The plague bacteria is transmitted to humans through bites of flea that previously fed on an infected animal, usually rat or other rodent.

Spanish flu

The deadliest flu pandemic in recorded history that spread throughout the world at the end of World War I in 1918 infected about one third of world’s population. The flu pandemic was caused by H1N1 influenza virus, the same strain that caused the so-called swine flu pandemic in 2009. Fortunately, the black scenario did not happen and in August 2010, the World Health Organization (WHO) announced the end of the swine flu pandemic.

Seasonal flu

Every year, seasonal flu claims about 500,000 lives worldwide despite the availability of flu vaccine which has been shown to be an effective preventive measure. The disease which can be caused by one of three influenza viruses called A, B and C is especially dangerous for young children, the elderly, pregnant women and people with chronic illnesses and weakened immune system. Otherwise healthy people usually recover within a few days.


The disease which is most often caused by Mycobacterium tuberculosis could pose a major health concern in the future worldwide due to increased antibiotic resistance of the tuberculosis bacteria. The disease which spreads through tiny droplets of saliva which are released into the air when an infected person sneezes, coughs or talks is most common in Asia and Africa. In 2010, tuberculosis killed about 1,5 million people, mostly in the developing countries.


The disease which is caused by a parasite from the genus Plasmodium is responsible for about 1 million deaths worldwide every year. It is transmitted through a bite of an infected mosquito and is often fatal for young children. It is rare outside the tropical areas but there are concerns that it could spread to temperate areas in case of climate change. No vaccine has been developed so far, while the available treatments are not always effective.


This bacterial disease spreads through contaminated water and kills more about 100,000 people every year. It has been virtually eliminated in the developed countries but it is still relatively common in poor countries where people often live in crowded and unhygienic conditions. It can easily be treated by rehydration, intravenous fluids and if necessary, antibiotics. It is crucial, however, to receive medical help promptly because death can occur in a matter of hours.


The systemic autoimmune disease which is caused by the human immunodeficiency virus (HIV) has killed more than 25 million people worldwide since it was first discovered in 1981. The condition cannot be cured but new medications have dramatically reduced death rate in the developed countries. In poor nations where health care is accessible only to the wealthy minority, mortality rate remains extremely high. Safe sex and the use of sterile needles remain the only HIV prevention measures.


This type of hemorrhagic fever is caused by one of four known ebolaviruses and causes sporadic outbreaks in Africa. It has not killed as many people as the above mentioned diseases, however, it is almost always fatal. A few people that survived the deadly disease needed months to recover completely. No cure or vaccine exists for ebola which spreads through contact with infected blood and body secretions.


The disease which meets all the criteria of pandemic except that it is not contagious is currently the most deadly disease in the world. According to the WHO, as many as 7.6 million people died from cancer worldwide in 2008. It can often be cured if discovered and treated early but unfortunately, many types of cancer do not cause any signs or symptoms until the disease has progressed. According to some experts, every third person will develop cancer at some point of life.