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Black Death Aids



In Africa Aids is proving a real scourge, in Europe less so.



New research suggests that Europeans have inherited a resistance to Aids because of the devastating effects of the bubonic plague. Science In Action reports.



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In the battle against Aids, scientists have acquired what looks like a potent new weapon. HIV, the virus that causes Aids, doesn’t infect everybody. Some people are simply born immune.



It’s all down to their particular genetic make-up and researchers are beginning to understand where that genetic protection comes from.



Stephen O’Brien from the US National Cancer Institute has discovered that a mutant form of one particular gene, called CCR5, confers protection against HIV.



That same gene variant may well have arisen in Europe, as a direct response to the Black Death.



Genetic distribution



The idea comes from a careful analysis of where in the world this particular gene variant shows up.



According to the researchers the mutation is absent in Africa and throughout East Asian populations and evident in varying amounts across Europe. O’Brien explains:



‘It was present as high as 15% in Scandinavia; it was less in Europe, about 10% in France, Germany and England. Further south it was 5% and in Saudi Arabia and Sub-Saharan Africa it was 0%.’



Believing that this ‘genetic drift’ was probably not random, the scientists looked to their history books to find out when this mutation was last prevalent in human history and what conditions may have favoured it.



The Black Death



Using the tools of molecular population genetics to identify exactly when the allele was last in force, the researchers were able to estimate that the gene variant was under a strong selection advantage approximately 700 years ago.



This period coincided with the period in history when bubonic plague was sweeping through Europe.



The Black Death, as it was known, started in Italy in 1347 and during the next three years it moved across Europe, killing perhaps as many as three-quarters of the people it infected.



The disease itself is thought to be bubonic plague, which is caused by a bacterium carried on the backs of rats. It can also be passed directly from human to human, which can result in death occurring within three days.



The Black Death was so named as sufferers displayed a range of symptoms including the lymph nodes swelling with pus and breaking the blood vessels under the skin. This caused internal bleeding and turned the skin black.



This outbreak of the Black Death lasted for over 300 years, killing at least 25 million people until it disappeared in 1670. However bubonic plague is a disease that still shows up every year in thousands of cases throughout Africa, Asia and the Americas.



Bacterial similarities



Whilst the researchers can not be certain that bubonic plague drove the mutated gene to such a high level, the study has unearthed some intriguing similarities between Aids and the Black Death. O’Brien explains:



‘There are hundreds of different tissues that viruses or bacteria can infect. Both HIV and yersinia pestis, the bacteria that causes Black Death, interestingly attack exactly the same tissues.’

‘The fact that precisely the same cells are the targets of this virus, the fact that the timing of this mutation is exactly when there was Black Death maybe indirect, but I think that they are telling coincidences that make the Black Death the most likely candidate for selective pressure.’



O’Brien now plans to work with scientists in Paris to establish if the presence of CCR5 in mice will lead them to be resistant to plague infection.



Meanwhile it is hoped that this research could have implications for new approaches to HIV- Aids treatments. Which could be good news for those in areas of the world, such as Africa, where levels of CCR5 in its mutant form are known to be low.



In the battle against Aids, scientists have acquired what looks like a potent new weapon. HIV, the virus that causes Aids, doesn’t infect everybody. Some people are simply born immune.It’s all down to their particular genetic make-up and researchers are beginning to understand where that genetic protection comes from.Stephen O’Brien from the US National Cancer Institute has discovered that a mutant form of one particular gene, called CCR5, confers protection against HIV.That same gene variant may well have arisen in Europe, as a direct response to the Black Death.The idea comes from a careful analysis of where in the world this particular gene variant shows up.According to the researchers the mutation is absent in Africa and throughout East Asian populations and evident in varying amounts across Europe. O’Brien explains:‘It was present as high as 15% in Scandinavia; it was less in Europe, about 10% in France, Germany and England. Further south it was 5% and in Saudi Arabia and Sub-Saharan Africa it was 0%.’Believing that this ‘genetic drift’ was probably not random, the scientists looked to their history books to find out when this mutation was last prevalent in human history and what conditions may have favoured it.Using the tools of molecular population genetics to identify exactly when the allele was last in force, the researchers were able to estimate that the gene variant was under a strong selection advantage approximately 700 years ago.This period coincided with the period in history when bubonic plague was sweeping through Europe.The Black Death, as it was known, started in Italy in 1347 and during the next three years it moved across Europe, killing perhaps as many as three-quarters of the people it infected.The disease itself is thought to be bubonic plague, which is caused by a bacterium carried on the backs of rats. It can also be passed directly from human to human, which can result in death occurring within three days.The Black Death was so named as sufferers displayed a range of symptoms including the lymph nodes swelling with pus and breaking the blood vessels under the skin. This caused internal bleeding and turned the skin black.This outbreak of the Black Death lasted for over 300 years, killing at least 25 million people until it disappeared in 1670. However bubonic plague is a disease that still shows up every year in thousands of cases throughout Africa, Asia and the Americas.Whilst the researchers can not be certain that bubonic plague drove the mutated gene to such a high level, the study has unearthed some intriguing similarities between Aids and the Black Death. O’Brien explains:‘The fact that precisely the same cells are the targets of this virus, the fact that the timing of this mutation is exactly when there was Black Death maybe indirect, but I think that they are telling coincidences that make the Black Death the most likely candidate for selective pressure.’O’Brien now plans to work with scientists in Paris to establish if the presence of CCR5 in mice will lead them to be resistant to plague infection.Meanwhile it is hoped that this research could have implications for new approaches to HIV- Aids treatments. Which could be good news for those in areas of the world, such as Africa, where levels of CCR5 in its mutant form are known to be low. More Highlights Beetle back juice The Bengal Tiger: spirit of the forest The dinosaur eating super-croc Marrakech climate talks Black Death Aids Left-handed memories Grading anthrax Nobel medicine man Global biological fears Bombing: the long-term fears Mapping the plague India obesity fears Racing to save the environment Family planning in Bangladesh Water tracking bacteria Chemical weapons of war ID cards: Facing the future The threat of asbestos In search of the missing in America New York health fears New York attempts to identify its missing High-tech hunt for low-tech man Black box: finding the perpetrators Super-skyscraper safety Coping with post-traumatic stress disorder Mobile safety fears Aids vaccine hope Gene Pioneers Ancestral lines Mobile phone movement Self repairing teeth Himalayan earthquake forecast Go Digital Starfish eyes Canadian bear necessities Healing hearts World water symposium Rain remover Dam Busters Population Predictions

Aids in Africa An estimated 4.7 million South Africans are HIV-positive, about 11% of the population.



Africa has been hardest hit by HIV, with an estimated 25 million infected people, equivalent to two-thirds of the world's cases, UN figures claim. Related Stories 22 October, 2001

Rebekka Armstrong: The face of Aids 08 October, 2001

Mapping the plague 07 September, 2001

Aids vaccine hope 02 August, 2001

Catching The Black Death Internet Sites The Black Death National Cancer Institute Adults living with HIV and Aids in Sub-Saharan Africa UNAIDS The BBC is not responsible for the content of external Internet sites