Eli5 Why does your immune system kill all of some viruses, but not others?

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When you get a cold or the flu your body kills all of the virus, but when you get herpes it stays in you for the rest of your life. Why does your body completely kill some viruses but not others?

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Anonymous 0 Comments

It has more to do with the viruses themselves than your immune system. There are two main types of viruses. RNA viruses and DNA viruses. RNA viruses replicate quick and It’s fairly easy for your immune system to find these viruses or the cells that they’re replicating in and destroy them. DNA viruses on the other hand write themselves into the DNA of your cells and hide from your immune system. HIV and Herpes are both examples of permanent diseases you get from viruses hiding inside your genetic code

Anonymous 0 Comments

It’s entirely dependent on the virus. Your immune system has broad ways to deal with viruses, but some viruses have very effective methods to evade detection. These methods vary greatly, and going into all possibilities is well outside the scope of ELI5.

Anonymous 0 Comments

The other commenter isn’t entirely correct.

Viruses that stay with you for your whole life use a few different strategies.

HIV is one example. It is a type of RNA virus called a retrovirus, meaning it has an enzyme called reverse transcriptase that will copy and paste it into your own DNA, so your body can’t get rid of it. Even if all the virus particles were to be magically scooped out of your body, your own cells would make more because of the virus DNA inserted into them. [Here’s some more info about retroviruses.](https://www.britannica.com/science/retrovirus)

Herpes, as you bring up, is another example. Herpesviruses stick around in the body by hiding from the immune system. Most types of herpesvirus infect neurons, which the immune system doesn’t patrol as aggressively. These viruses can also mimic human cell surface molecules to try and hide better. [Wikipedia has a chart](https://en.wikipedia.org/wiki/Herpesviridae#Immune_system_evasions) showing some common types of herpes virus and where they hide out. Chicken pox and CMV (cytomegalovirus) are two well known examples.