Virus

Definition

A virus is a microscopic infectious agent that can only replicate inside the living cells of an organism. Viruses consist of genetic material (DNA or RNA) enclosed in a protein coat.

5 Must Know Facts For Your Next Test

1. Viruses are obligate intracellular parasites, meaning they require a host cell to replicate.
2. The structure of a virus includes genetic material, a protein coat called a capsid, and sometimes a lipid envelope.
3. Viruses can infect all types of life forms, from animals and plants to bacteria and archaea.
4. Viral infections can range from asymptomatic to causing severe diseases such as influenza, HIV/AIDS, and COVID-19.
5. Antibiotics are ineffective against viruses; antiviral drugs or vaccines are used for prevention and treatment.

Review Questions

• What is the basic structure of a virus?
• Why can't viruses replicate outside of living cells?
• How do antiviral drugs differ from antibiotics?

Related terms

Bacteriophage:

A type of virus that infects bacteria.

Capsid:

The protein coat surrounding the genetic material of a virus.

Host Cell: A living cell in which a virus replicates.