The ongoing Ebola epidemic has sparked fears around the world, in part due to the horrific symptoms associated with the disease and the current lack of cure.
It has killed more than 11,000 people since December 2013, in by far the largest recorded outbreak of the deadly virus. While the epidemic originated in West Africa, cases of the disease have appeared in the U.S., Spain and Germany.
However, diseases such as tuberculosis and malaria also remain endemic in many parts of the world, and HIV/AIDS continues to blight much of sub-Saharan Africa. CNBC takes a look at some of the worst epidemics throughout the ages.
—By CNBC's Katy Barnato. Updated on Thursday July 2015.
Smallpox is a very old disease, dating back to Egyptian times. Before the disease was eradicated through inoculation, epidemics could kill 30 percent of those infected and cause scarring in the rest.
In Europe, the disease is estimated to have killed 60 million people in the 18th century alone. Its introduction into the Americas by European settlers in the 16th century killed almost all of the indigenous people. It is considered to be a major factor in the Spanish conquering the Inca and Aztec civilizations.
Smallpox was declared eradicated in 1980 following a global immunization campaign led by the World Health Organization (WHO). The last known natural case was in Somalia in 1977. Since then, the only known cases were caused by a laboratory accident in 1978 in Birmingham, England, which killed one person and caused a small outbreak.
Tuberculosis, also known as consumption or TB, has also been around for a very long time—with evidence of the disease found in some Egyptian mummies from 3,000-2,400 BC.
TB killed more people than any other disease during the 19th and early-20th centuries, according to the Harvard University Library. It is caused by a bacterium called Mycobacterium tuberculosis which usually attacks the lungs, but can also hit other parts of the body such as the kidney, spine, and brain.
By the late 19th century, between 70 and 90 percent of the urban populations of Europe and North America were infected with the TB bacillus, and about 80 percent of those individuals who developed active tuberculosis died of it.
Today, TB is rare in wealthier countries, but second only to HIV/AIDS as the greatest killer worldwide, according to the WHO. In 2012, 8.6 million people fell ill with TB and 1.3 million died from it.
People with weak immune systems, for instance due to HIV, have a much higher risk of falling ill with TB. Hence TB is common in countries with high numbers of HIV/AIDS suffers.
Malaria is still a major problem in developing countries, particularly in sub-Saharan Africa, where around 90 percent of all deaths from the disease occur. WHO estimates that in 2012, there were around 207 million malaria cases across the world, resulting in 627,000 deaths.
Malaria was once endemic in Europe, but was eradicated during the 20th century. However, cases have reappeared in Greece since 2009.
The disease is caused by parasites that are transmitted to people through the bites of infected mosquitoes.
The Plague of Justinian in 541-543 AD is history's first recorded pandemic—an epidemic that occurs over a very wide area and affects a large number of people.
It was named after Justinian, the emperor of the Byzantine Empire (Eastern Roman Empire). The outbreak originated in Ethiopia and spread throughout the empire. The 541 AD pandemic was followed by frequent outbreaks over the next two hundred years, eventually killing over 100 million people across the European Mediterranean.
We now know that plague is caused by a bacterium called yersinia pestis that often infects small rodents like rats, mice, and squirrels. It is usually transmitted to humans through the bite of an infected flea.
Cholera is an acute infection picked up from contaminated food or water. It first hit Europe and North America between 1831 and 1832, but originated centuries before in India. Symptoms include violent cramps, vomiting and diarrhea.
Epidemics trickled out towards the end of the 19th century in Europe and the U.S., but continue to hit poorer countries. The WHO estimates there are still 3-5 million cholera cases a year. "Recently, the re-emergence of cholera has been noted in parallel with the ever-increasing size of vulnerable populations living in unsanitary conditions," the organization said on its website.
The Black Death—then known as the "great pestilence"—arrived out of central Asia in the mid-1300s, spreading through trading routes to Europe, Asia and parts of Africa. It killed around 30 percent of Europe's populace and half of the people in China.
On top of disease and death, the plague also brought fear, panic and upheaval. In England, the shortage of workers helped to bring an end to the "fief" system whereby people were servants of the landowner.
Smaller epidemics continued through the centuries, with the last major one in England in 1665.
Between 50 and 100 million people across the world died from "Spanish" influenza between 1918 and 1919—far more than the 16 million killed in the preceding World War I.
The name Spanish Influenza came about because the Spanish media published uncensored reports of the pandemic, compared to other European governments which controlled the news for fear of undermining public morale.
An estimated 500 million people across the world caught flu during the three waves of this epidemic.
Influenza viruses continue to evolve and flu epidemics strike fear to this day. Recently, the 2009 "swine flu" killed up to 576,000 people in Mexico and the south of the U.S..
Polio, or paralytic poliomyelitis to give it its full name, is a viral disease that affects the nervous system and can lead to paralysis and death.
The disease reached pandemic proportions in the 1940s and 1950s across Europe, North America, Australia and New Zealand. The outbreaks created panic and led to travel bans between cities in the U.S.
At the disease's height in 1952, 3,145 Americans died from polio and 21,269 were left paralyzed.
Records from antiquity mention crippling diseases compatible with polio, but the first outbreaks in Europe and the U.S. were not reported until the 19th century.
Vaccines are now available against polio and there are hopes the virus will be eradicated across the world within the next decade.
HIV, the virus that causes "acquired immunodeficiency syndrome" (AIDS), has become one of the world's most serious health challenges since it was first reported in 1981.
Since then, around 75 million people across all regions of the world have contracted HIV. Sub-Saharan Africa remains most severely affected, with nearly 1 in every 20 adults living with HIV, according to the WHO.