What is a Virus?

Viruses are tiny organisms that may lead to mild to severe illnesses in humans, animals and plants. This may include flu or a cold to something more life threatening like HIV/AIDS.

What is a virus?

Viruses cause these diseases — and many more. Some are serious. Others, not so much. For better or worse, viruses are part of life.  It surprises many people to learn that viruses “live” in us but aren’t technically alive. Viruses can replicate only inside the cells of their host. A host can be an animal, plant, bacterium or fungus.  Viruses are sometimes confused with another family of germs: bacteria. But viruses are much, much smaller. Think of a virus as a tiny package inside a tiny protein coat. Inside is either DNA or RNA. Each molecule serves as an instruction book. Its genetic information provides instructions that tell a cell what to make and when to make it.  When a virus infects a cell, it sends that cell a simple message: Make more viruses.

How big are viruses?

The virus particles are 100 times smaller than a single bacteria cell. The bacterial cell alone is more than 10 times smaller than a human cell and a human cell is 10 times smaller than the diameter of a single human hair.

Are viruses alive?

Viruses by themselves are not alive. They cannot grow or multiply on their own and need to enter a human or animal cell and take over the cell to help them multiply. These viruses may also infect bacterial cells.
The virus particle or the virions attack the cell and take over its machinery to carry out their own life processes of multiplication and growth. An infected cell will produce viral particles instead of its usual products.

Structure of a virus

A virion (virus particle) has three main parts:
Nucleic acid – this is the core of the virus with the DNA or RNA (deoxyribonucleic acid and ribonucleic acid respectively). The DNA or RNA holds all of the information for the virus and that makes it unique and helps it multiply.
Protein Coat (capsid) – This is covering over the nucleic acid that protects it.
Lipid membrane (envelope) – this covers the capsid. Many viruses do not have this envelope and are called naked viruses.