What are Viruses?
Viruses are infectious agents that can only replicate inside the cells of living organisms. They are made up of genetic material (either DNA or RNA) enclosed in a protein coat.

Characteristics of Viruses
- Viruses are not considered living organisms as they cannot carry out metabolic processes on their own.
- They lack the ability to reproduce outside of a host cell.
- Viruses can infect a wide range of organisms, including humans, animals, plants, and bacteria.

Structure of Viruses
- Viruses have a simple structure consisting of genetic material (DNA or RNA) enclosed in a protein coat called a capsid.
- Some viruses also have an outer lipid envelope derived from the host cell membrane.

Mode of Infection
- Viruses infect host cells by attaching to specific receptors on the cell surface and injecting their genetic material into the cell.
- Once inside the cell, the virus hijacks the host cell's machinery to replicate itself.

Impact of Viruses
- Viruses can cause a wide range of diseases in humans, including the common cold, flu, HIV/AIDS, and COVID-19.
- They can also infect plants and animals, leading to economic losses in agriculture and livestock industries.

Prevention and Treatment
- Vaccines are an effective way to prevent viral infections by stimulating the immune system to produce antibodies against specific viruses.
- Antiviral medications can help treat viral infections by targeting different stages of the viral replication cycle.