Since the topic of HIV comes into many conversations on this forum, I thought it would be nice to explain what HIV, or, human immunodeficiency virus actually is and how it works.

Firstly, I'll start by explaining how most virulent viruses work. A virus is a non-living, infectious agent which contains nucleic acids (DNA) with a coat of protein (referred to as a caspid) on the outside the viral DNA (inside the membrane) which is all surrounded by a membrane. The virus will dock onto a host cell, and insert its DNA into the host cell.

From this point, the virus may take enter one of two cycles: the lytic cycle, or, the lysogenic cycle. In the lytic cylce, the DNA acts as a separate molecule from the host's DNA and replicates its DNA on its own. When too many viruses have been made in the host cell, the host cell's membrane will split, or, lyse (hence lytic cycle) and cause the viruses to exit the cell and infect other cells.

In the lysogenic cycle, the viral DNA will become integrated into the host cell's DNA, and every time the host cell DNA is replicated, so too is the viral DNA.

It is very important that viruses use DNA, as DNA has many "proof-reading" mechanisms to prevent mutations. If the genetic material is in the form of RNA instead of DNA however, things are much different. RNA lacks the proof-reading mechanisms that DNA has, and so its rate of mutation will be a lot higher. Viruses which inject RNA are referred to as retroviruses.

Retroviruses contain RNA instead of DNA, along with an enzyme called reverse transcriptase, which catalyzes the production of DNA from RNA (note the lack of proof-reading mechanisms as mentioned earlier). Since the rate of mutation is very high, the genome of the retrovirus is constantly changing and mutating as the number of viruses in one's system rise exponentially.

HIV is a retrovirus, which is the reason there is no vaccine for HIV; by the time a vaccine is ready, that vaccine will be outdated as the HIV virus already has mutated many different times.

Here's a cartoon depicting a HIV virus:


The only way to stop a retrovirus would be to find a way to stop reverse transcriptase from working, which is not as easy as it sounds.

Hope this was helpful.