The world is at risk of another life-threatening global pandemic, comparable to outbreaks in the past that have wiped out hundreds of millions of people, according to the World Health Organisation’s director general.

Tedros Adhanom issued the stark warning at the World Government Summit this week. “This is not some future nightmare scenario. This is exactly what happened, 100 years ago during the Spanish flu epidemic in 1918,” he said, emphasising the importance of universal health coverage in staving off the global threat.

Adhanom admitted that it is not known when and where the next global pandemic might occur but insisted it would “take a terrible toll, both on human life, and on the global economy,” as previous deadly widespread diseases have done before.

With this stark warning now before us, RT looks back at some of the deadliest pandemics to spread across the globe, leaving devastating death tolls in their wake.

1. The Black Death

Death toll: 50 million plus

Perhaps the most infamous pandemic of all is the Black Death, often referred to simply as ‘The Plague,’ which ravaged Europe before spreading into Asia in the 14th century.

It caused more than 50 million deaths in Europe alone, according to WHO. The Black Death was believed to have originated in Asia and thought to have spread through rats and fleas. Modern scientific research has dismissed this, however, and disputes whether it was the bubonic plague.

2. The Spanish Flu

Death toll: 50 million plus

The Spanish Flu described by Adhanom as the “deadliest outbreak in recorded history” spread quickly across the globe towards the end of World War I in 1918. Despite its name, it didn't originate in Spain and was first identified in a US military camp in Kansas.

More than 50 million people are estimated to have died from the disease. Approximately 25 million of those deaths came in the first 25 weeks of the outbreak. Half a billion people were infected.

3. Plague of Justinian

Death toll: 25 million plus

The Plague of Justinian is believed to have been a bubonic plague that originated when a ship with rat-infested grain arrived in Constantinople, the capital of the Byzantine Empire in the year 541 AD.

As many as 5,000 people died per day in Constantinople at the peak of the disease in 542 AD. It’s estimated that 25 million people died during the period - wiping out a quarter of the eastern Mediterranean population.

The plague continued to spread through Europe and onto Asia and Africa. Later epidemics between the years 542 and 546 in Asia, Africa and Europe killed nearly 100 million people.

Death on a slow fuse: Only a matter of time before next pandemic hits us – study https://t.co/MqQDrX3wxbpic.twitter.com/KQ81xejYIH — RT (@RT_com) May 25, 2017

4. Antonine Plague - Smallpox

Death toll: 5 million plus

The Antonine Plague, also known as the Plague of Galen, flared up in the Roman Empire in 165 AD after Roman soldiers returned from Mesopotamia (modern day Iraq).

The ancient pandemic affected Asia Minor, Egypt, Greece, and Italy. It decimated the Roman army and killed over 5 million people.

It’s thought the disease was what we know today as smallpox. The ancient disease was officially declared eradicated in 1979. It’s estimated that the global death toll from smallpox during the 20th century could have reached around 300 million.

5. HIV/Aids

Death toll: 36 million

A pandemic that we are still battling, HIV has claimed 36 million lives across the globe, according to WHO. One million people died in 2016 from HIV-related causes.

The human immunodeficiency virus (HIV), which attacks the body’s immune system, was discovered in 1984. It’s believed to have originated from a virus affecting chimpanzees in west central Africa. Scientists say the virus was most likely transmitted to humans and mutated into HIV when humans hunted these chimpanzees for meat and came into contact with their infected blood.

More than 5,600 people worldwide become newly infected with HIV every day, according to the International Aids Vaccine Initiative.

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