New diseases may occur from natural sources and, on occasion, from experiments in a laboratory. It should also announced that the biggest part is made by new, natural diseases. These begin when viruses or bacteria that infect animals spreads to people, which usually occurs when human are more in contact with animals or their products than they used to be. It may occur where forests are cleared, people capture wild animals or when pig, cattle etc rearage is increased. Another factor is climate change because heat contributes to the germs’ spread. In some occasions, laboratories that deal with viruses develop some mishaps, though this is rare a times. In many cases, diseases are not caused by humans, but rather they develop because of alterations in the climate, contacts with animals or modifications of behavior.