Viruses are devious.
They consist of small pieces of genetic code, whether in the DNA or RNA form, and little else. They work by hijacking the life systems of living cells and forcing them to create more copies of the virus.
They are the cause of many of the worst diseases. HIV, influenza, smallpox, polio, rabies, hepatitis, yellow fever – and many more are caused by viruses.
Are they alive? Technically no as they can do nothing by themselves, but it is not a simple yes/no question with them.
What’s fascinating about them is how efficient they are. Humans use almost none of their genetic code; something like 1%. Depending how you look at it, some viruses could be argued to use more than 100% of their code.
They are, for instance, able to create proteins that have one function but can be easily switched into another form that does something else entirely. Also, their genetic code can code for one set of proteins, but with a minor switch, code for another set entirely.
This hyperefficency allows viruses extremely complex and powerful abilities.
We have very few treatments that help someone who is infected with a virus. We are often only able to give supportive care, while having limited ability to treat the actual disease.
Vaccines, however, can prevent the infection from happening. They work by exposing someone to elements of a virus in a controlled and generally safe manner. Their body develops an immune response to the virus, which allows it to respond rapidly and effectively when it attempts to attack them in real life.
Some disease are hard to develop vaccines for like HIV/AIDs. This is due to the complexity of the virus, which actually acts to target immune cells. A strong immune response might sadly strengthen the virus.
How viruses work
There are many ways that viruses work. Many work by injecting themselves into a cell and then immediately hijacking internal factories to produce their products. These include poliovirus.
Others infect the cell but first have to create the right coding sequences to use the cell’s genetic equipment. These include influenza.
The more complex viruses don’t restrict their activity to the outer region of the cell known as the cytoplasm. Some inject themselves into the more restricted nucleolus, where the host’s DNA is kept.
The retroviruses in particular come in as the RNA form, turn themselves into DNA, then add themselves into the host.