Although only about one person in ten with a positive skin test or blood assay ever develops. TB disease, the risk continues throughout the rest of your life. The symptoms of TB are. common to many other illnesses.
Marco Polo-Great Silk Road. For many centuries the Great Silk Road connected a complex network of trade routes from Europe with Asia. It was a way to establish contact with the great civilizations of China, India, the Near East and Europe.
Marco Polo (1254â1324) traveled along the Silk Road visiting the Yuan capital city Dadu (today's Beijing). In his famous book about the Orient he mentions a special passport in the form of a board. It was issued by the Yuan government to the merchants to protect their trade and free movement within the country.