user45525: Are "virus" and "virology" sufficiently different to justify two tags?
Similarly, is there a reason to have narrow tags like "retrovirus" and "lentivirus", especially when there is no tag "bacteriophage"?
Would it not make more sense to have a single tag such as "virology" (all things related to viruses), and maybe something about "viral-vectors" for things that focus on lentiviral transduction, phage-mediated directed evolution and other things that are not about natural viruses?

user3340: virus is a synonym of virology; so any question tagged with the former will automatically be tagged as virology. 
Regarding whether lentivirus or retrovirus are really needed: perhaps they may be useful in the context of the cell biology techniques (viral transduction) and diseases caused by retroviruses. Both of these are important areas of research. 
Bacteriophage can also have a tag on it's own. If you have questions specifically related to bacteriophages then you can create a tag. All users above the reputation of 300 can create new tags. 

45525: <p>Are "virus" and "virology" sufficiently different to justify two tags?
Similarly, is there a reason to have narrow tags like "retrovirus" and "lentivirus", especially when there is no tag "bacteriophage"?</p>

<p>Would it not make more sense to have a single tag such as "virology" (all things related to viruses), and maybe something about "viral-vectors" for things that focus on lentiviral transduction, phage-mediated directed evolution and other things that are not about natural viruses?</p>
 3340: <p><a href="https://biology.stackexchange.com/questions/tagged/virus" class="post-tag" title="show questions tagged &#39;virus&#39;" rel="tag">virus</a> is a synonym of <a href="https://biology.stackexchange.com/questions/tagged/virology" class="post-tag" title="show questions tagged &#39;virology&#39;" rel="tag">virology</a>; so any question tagged with the former will automatically be tagged as <a href="https://biology.stackexchange.com/questions/tagged/virology" class="post-tag" title="show questions tagged &#39;virology&#39;" rel="tag">virology</a>. </p>

<p>Regarding whether <a href="https://biology.stackexchange.com/questions/tagged/lentivirus" class="post-tag" title="show questions tagged &#39;lentivirus&#39;" rel="tag">lentivirus</a> or <a href="https://biology.stackexchange.com/questions/tagged/retrovirus" class="post-tag" title="show questions tagged &#39;retrovirus&#39;" rel="tag">retrovirus</a> are really needed: perhaps they may be useful in the context of the cell biology techniques (viral transduction) and diseases caused by retroviruses. Both of these are important areas of research. </p>

<p>Bacteriophage can also have a tag on it's own. If you have questions specifically related to bacteriophages then you can create a tag. All users above the reputation of 300 can create new tags. </p>
