Question

Which cause infectious disease?

Answer 1

Which case infectious disease?
Infectious diseases are transmitted in different ways:

Direct contact
By airways
By the digestive tract
By animal bites or stings
The development of an infectious disease epidemic or endemic retention depends both infectious germ of the population in contact and their environment.
A contagious disease appears when the virulence of the microbe (its ability to multiply and cause unrest in the body) exceeds the individual's defense (immune).
Infection can occur through direct contact from an individual (sick or not) carrying the microorganism, or from an animal. It may be effected by indirect contact with the environment, or via an insect.