Changes

== Classification ==

== Classification ==

Viruses are classified based on several characteristics:<br />

Viruses are classified based on several characteristics:<br />

The type of nucleic acid (DNA vs RNA) <br />

The type of [[nucleic acid]] ([[DNA]] vs [[RNA]]) <br />

The strandedness of that acid (single strand vs double strand)<br />

The strandedness of that acid (single strand vs double strand)<br />

The content of their protein capsids<br />

The content of their [[protein]] capsids<br />

The hosts they are able to infect.<br />

The hosts they are able to infect.<br />

The presence or absence of an envelope around the capsid (a lipid layer derived from host cell membranes with embedded proteins).<br />

The presence or absence of an envelope around the capsid (a [[lipid]] layer derived from host cell membranes with embedded proteins).<br />

Viruses which infect bacteria are referred to as "bacteriophages".

Viruses which infect [[bacteria]] are referred to as "bacteriophages".

==Forms of replication==

==Forms of replication==

'''Lytic'''<br />

'''Lytic'''<br />

The first step to viral replication is entry into the cell. The virus uses proteins in either its capsid or envelope to bind to a protein on the surface of the cell. Each virus can only use certain proteins which influences which cells they are able to infect (a property called 'tropism'). One inside, the virus must shed its protein coat and prepare to be replicated. The process of replication will differ based upon whether or not the virus is DNA based or RNA based. Following replication virus particles self assemble and leave the cell, either by bursting through the membrane or budding off leaving the membrane intact.

The first step to viral replication is entry into the cell. The virus uses proteins in either its capsid or envelope to bind to a protein on the surface of the cell. Each virus can only use certain proteins which influences which cells they are able to infect (a property called '[[tropism]]'). One inside, the virus leaves behind its protein coat in the cell wall and prepares to be replicated. The process of replication will differ based upon whether or not the virus is DNA based or RNA based. Following replication virus particles self assemble and leave the cell, either by bursting through the membrane or budding off leaving the membrane intact.

'''Lysogenic'''<br />

'''Lysogenic'''<br />

==Are viruses alive?==

==Are viruses alive?==

There is disagreement on whether or not viruses should be considered alive since they do not share many of the processes that other forms of life have. They do not feed, respire, grow, reproduce through cell division, or move under their own power. Viruses also do not have a cell structure, despite having genes.  In general, they are labeled as non-living, since they do not meet the common criteria for life.<ref>http://sphweb.bumc.bu.edu/otlt/MPH-Modules/PH/PH709_InfectiousAgents/PH709_InfectiousAgents8.html</ref>

There is disagreement on whether or not viruses should be considered alive since they do not share many of the processes that other forms of [[Life (biology)|life]] have. They do not feed, respire, grow, reproduce through cell division, or move under their own power. Viruses also do not have a cell structure, despite having genes.  In general, they are labeled as non-living, since they do not meet the common criteria for life.<ref>http://sphweb.bumc.bu.edu/otlt/MPH-Modules/PH/PH709_InfectiousAgents/PH709_InfectiousAgents8.html</ref>

==Examples==

==Examples==

Examples of viruses that infect [[human]]s include the [[influenza]] virus, the common cold, [[HIV]], [[smallpox]] and [[polio]].

Examples of viruses that infect [[human]]s include the [[influenza]] virus, the [[common cold]], [[HIV]], [[smallpox]] and [[polio]].<br />

 

Viruses can also attack [[bacteria]]. These viruses are called bacteriophages.

Viruses that attack [[bacteria]] are called bacteriophages.

==Immunities==

==Immunities==

Viruses are not targeted by [[antibiotics]], the drugs used to kill [[bacteria]], and so use of antibiotics for viral infections is usually inappropriate.  There are, however, some antiviral drugs used in cases of viral infection; most notably acyclovir, interferon, and ribavarin.  These anti-viral drugs are usually used only in severe cases, since they tend to have strong side-effects.<br />

Viruses are not targeted by [[antibiotics]], the drugs used to kill [[bacteria]], and so use of antibiotics for viral infections is usually inappropriate.  There are, however, some antiviral [[drug]]s used in cases of viral infection; most notably acyclovir, interferon, and ribavarin.  These anti-viral drugs are usually used only in severe cases, since they tend to have strong side-effects.<br />

Many viral infections such as the common cold (from Rhinoviruses) are simply left to the human's or animal's immune system to be eradicated.  The immune system is often strengthened with [[vitamin]], [[mineral]], and [[herb]]al supplements to expedite the removal process.  These are also sometimes used to keep retroviruses dormant.

Many viral infections such as the common cold (from Rhinoviruses) are simply left to the human's or animal's immune system to be eradicated.  The immune system is often strengthened with [[vitamin]], [[mineral]], and [[herb]]al supplements to expedite the removal process.  These are also sometimes used to keep retroviruses dormant.