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.

Cholera

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.

HIV/AIDS

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.

Ebola

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.