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
The people of Rome could go into the Colosseum without any costs; it was free. In the Middle Ages it was no longer used for performances. It was then used as housing, workshops, a Christian shrine, and as a supply of building stones. It is now a ruin because of earthquakes. The Colosseum is a symbol of the Roman Empire. It is one of Rome's most popular tourist attractions.