Topic 2.3
What are viruses?
Viruses are unique infectious agents that differ from bacteria and other pathogens. They cannot survive or reproduce on their own. Instead, viruses need to enter a host cell, where they hijack the cell’s machinery to replicate. This page will explore virus structure, how they infect cells, and examples of viral infections.
Viruses
Viruses are much smaller than bacteria. They are, by definition, not living and can only survive inside another cell. Viruses attack specific cells – the flu virus targets and attacks cells in the respiratory system (throat and lungs). Once the virus infects a cell, it starts to replicate until it fills the cell and causes it to burst. Examples of viruses include SARS-CoV2, measles, mumps, rubella, influenza, chickenpox and polio.
Virus Cell Structure
This illustration shows the main components of a virus, specifically SARS-CoV-2, the virus causing COVID-19:
- RNA (or DNA): Represented inside the virus, the genetic material (shown in grey) enables the virus to take control of the host cell.
- Protein Coat: The outer layer protects the RNA and aids cell attachment.
- S (Spike) Protein: The red spikes on the surface allow SARS-CoV-2 to enter human cells, making it a key target for vaccines.
Discussion
- Why are viruses considered non-living? Discuss what makes them different from living organisms and why they need a host to survive.
- What are the challenges in creating vaccines for different types of viruses? Consider factors like virus mutation rates and how they impact vaccine development.