The human body can be infected by many types of infectious agents, such as viruses, bacteria, fungi, and parasites. how are viruses, such as hepatitis, different from other types of infectious agents?

f) they need a warm environment to survive
g) they feed on the nutrients provided by the host
h) they cannot replicate without a host cell
j) they need protection from bacteria and other micro-organisms

The main difference between viruses and the other infection agents is that viruses can't replicate without a host cell. Viruses do not have their own metabolism, so they need a host cell to make a new product. Therefor, they are considered as a basic unit of life. There are different opinion, whether the viruses are a form of life or just organic structures that interact with living organisms, although they have genes and evolve by natural selection. They reproduce by creating multiple copies of themselves.