Viruses cannot reproduce on their own. They are obligate intracellular parasites, meaning they rely entirely on the host cell's machinery to replicate. When a virus infects a cell, it inserts its genetic material into the host cell and uses the cell's resources to create copies of itself. This process, called viral replication, continues until the host cell bursts, releasing new viral particles to infect other cells.
Here's how the process works:
- Attachment: The virus attaches to the surface of a host cell.
- Entry: The virus enters the host cell, often by injecting its genetic material or by being engulfed by the cell.
- Replication: The virus uses the host cell's machinery to make copies of its genetic material and proteins.
- Assembly: New viral particles are assembled from the newly synthesized components.
- Release: The new viral particles are released from the host cell, often killing the cell in the process.
Viruses have different ways of replicating. Some viruses use a lytic cycle, where they quickly replicate and destroy the host cell. Others use a lysogenic cycle, where they integrate their genetic material into the host cell's DNA and remain dormant for a period of time. This can lead to a prolonged infection or the development of cancer.
Examples of viral diseases include:
- Influenza
- Common cold
- COVID-19
- HIV
- Measles
- Mumps
- Rubella
- Hepatitis B
- Hepatitis C
