YDT Okuma Alıştırmaları

The name by which the bubonic plague came to be known, the Black Death, was related to the formation of black boils in the armpits, neck, and groin of infected people, which were caused by dried blood accumulating under the skin after internal bleeding. People infected with the bacterium of the Black Death, Yersinia pestis, first experienced symptoms such as chills, fever, vomiting, and diarrhoea. Frequently, the disease spread to the lungs and, almost always in these cases, the victims died soon afterwards. For reasons unknown at the time, some people never caught the disease although they were in close contact with those who had. In 2005, Dr Stephen O'Brien of the National Institutes of Health in Washington D.C. searched for descendants of the 17th-century survivors in London, England. He was able to locate a number of them, and from those people he took blood samples and recorded their DNA. He had been working with HIV patients, and to his great surprise, he discovered that the critical gene CCR5 that saved the lives of Black Death survivors was the same gene that today helps people infected with the HIV virus to survive.