Other viruses that can cause colds include coronavirus, respiratory syncytial virus, influenza and parainfluenza. Colds cause a lot of people to stay home. The CDC says 22 million school days are lost each year in the U.S. because of them. Some estimates say that Americans have 1 billion colds a year. For more detail, see Common Cold Causes. How a Common Cold Starts. You can catch it from another person who is infected with the virus. This can happen by direct physical contact with someone who has a cold, or by touching a surface contaminated with their germs -- like a computer keyboard, doorknob or spoon --- and then touching your nose or mouth.
The hypocaust system. The hypocaust system (hypocaustum in Latin) was a heating system used in (wealthy) Roman homes and Roman baths, and the closest thing to central heating today. The hypocaust was a system that circulated hot air under the floor and surrounding walls. Hypocaust construction
Ironically, Ostia was to play a major part in the downfall of Rome when Alaric the Goth captured Ostia in AD 409 knowing that this would starve Rome of much needed food. The Romans did what they could to make sea journeys safe â lighthouses were built as were safe harbours and docks. The Roman Navy did what it could to make the Mediterranean Sea safe from pirates. The Romans made trade as easy as possible. There was only one currency used and there were no complicating customs dues. Trade was also encouraged by many years of peace within the Empire. Trade was vital to the success of the Empire. When the Empire collapsed, trade throughout the lands that had once made up the Roman Empire, also collapsed.