Virology MIC252: Viral Pathogenesis

Study Notes

Course Focus: Viral entry into the human body, spread to other organs, and disease causation. The virus life cycle within a cell (entry, genome replication, gene expression, assembly, and release) is also covered. Cancer-causing viruses are discussed.
Required Textbook: Essential Human Virology by J. Louten (2016), available free via the UWC library.
Lecture 26: Viral Pathogenesis: Explains how viruses cause disease, enter the human body, spread within the body, transmission modes, and modified Koch's postulates for viruses.

Viruses are tiny (10-400 nm), infectious, obligate intracellular parasites.
They consist of genetic material (RNA or DNA) encased in a protein capsid, sometimes with a membrane.
Viruses lack protein synthesis; they are neither cells nor bacteria.

Traditional Koch's postulates establish a causal link between a microbe and a disease through four criteria.
These postulates are unsuitable for viruses because:
- Not all infected individuals show symptoms (e.g., polio).
- Different viruses can cause similar diseases.
- Many viruses are uncultivable in vitro.
- Suitable animal models mimicking human disease may be lacking.

Focus on identifying pathogen-associated nucleic acid sequences in diseased hosts, their absence (or lower numbers) in healthy hosts, and changes in copy numbers correlating with disease progression or resolution.

Viral Pathogenesis: The process by which viruses cause disease.
Viral Disease: The combined effects of viral replication and the host's immune response; influenced by both viral and host genes.
Many viral infections are asymptomatic or subclinical due to effective host immune control.
Some viruses evade immune responses, leading to severe disease. Sometimes, the immune response itself is responsible for disease symptoms.