A Virus is a small organism that is known to cause severe illnesses not only in humans, but also animals and plants.  There is a very wide range of viruses such as the flu, colds, tuberculosis, HIV or AIDS, all of which can be fatal.

3 part structure.

The Nucleic Acid is considered the core of the virus and contains its DNA or RNA.

The Protein Coat or capsid, is the protective covering that surrounds the nucleic acid.

The Lipid Membrane or envelope covers the capsid and is unique to each virus.  Some viruses have them others don’t.  Those that do not consist of a Lipid Membrane are also referred to as “naked viruses”.

A viruses life cycle is known as the lytic cycle.

The 1st stage is known as “absorption” and is when the virus attaches to a host cell.  In the 2nd stage, or “entry” stage, the virus injects its DNA or RNA into the host cell.  Stage 3 consists of the invading DNA taking over the hosts cell then recruiting its enzymes.  Stage 4 or the “replication” stage, the enzymes begin creating new virus particles.  

In Stage 5 These new virus particles then come together to create new viruses in a process known as “assembly”.  The 6th and Final Stage of the lytic cycle is also known as the “release”.  During this stage, the newly created viruses kill the host cell, allowing it to detach in search of a new host to infect.

Unable to survive on their own, the virus must invade a host cell in order to multiply and usually enter our bodies via other individuals, water, nose, mouth, and any cut or opening on the skin.  For example, colds and flu target respiratory and digestive cells while viruses such as HIV or AIDS target T-Cells in our immune system