Viral pathogenesis is the study of how biological viruses cause diseases in their target hosts, usually at the cellular or molecular level 1. Viruses have different sites of entry into a human body. They possess the ability to enter through the urinogenital tracts, eye, skin, respiratory tracts and alimentary tracts. the most common route of viral entry id through the respiratory tract. When we see respiratory tracts, we mean, through inhalation via nose.
viral pathogenesis depends on the complex interplay of a large number of virus and host factors. Viral factors include cell tropism and cellular pathogenesis. 2. There are various steps to the pathogenesis of a viral infection including attachment, uncoating, penetration, replication and release, as well as the lysogenic and lytic cycles. Viruses avoid body defense by multiplying within host cells, where antibodies and other components of the immune system cannot reach them. The courses of viral infection are primary replication, systemic spread and secondary replication.
Viral affinity for specific body tissues (tropism) is determine by cell receptors for virus, cell transcription factors that recongize viral promoters and enhancers sequencers. Ability of the cell to support virus replication, physical barriers, local temperature, pH, oxygen tension enzymes and non-specific factors in the body secretions and digestive enzymes and bile in the gastrointestinal tract that may inactivate some viruses.
The immune response is the most important host factor, as it determines whether the virus is cleared or not.
in viral infections, the host innate immune system is meant to act as a first line defense to prevent viral invasion or replication befoe more specific protection by the adaptive immune system is generated
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References
Viral Pathogenesis
Principles of Virology 4th Edition
Wikipedia