|The study of viruses and viral diseases.V iruses are organized associations of macromolecules nucleic acid contained within a protective shell of protein units .
On its own, a virus may be considered as an inert entity since it does not replicate outside of a living cell. Because viruses are non-motile, they are entirely dependent on external physical factors for chance movement and spread to infect other susceptible cells. Viruses co-evolve with their hosts.
They can be classified in several ways, such as by their geometry, by whether they have envelopes, by the identity of the host organism they can infect, by mode of transmission, or by the type of disease they cause.
In this lesson we will deal with viral