Herpes would be one example. There are treatments for it. But once you have it you have it for life, no? Why?
And HIV. With modern medicines you can get to the point where it is undetectable in your blood and other bodily fluids. Yet you’ll still have it for life. Why?
Because on the other end of the spectrum, there’s the cold virus. I can usually shake a cold virus in a couple of days. Again, in comparison to what I just said, why?
As I understand it, Herpes is a retro virus. Which means that it actually inserts itself into your own DNA, in the cells in the immediate area of the infection site. So it keeps popping up because now it is a part of you on a fundamental level.
Yup, and the same for HIV.
There are key differences between herpesviruses and retroviruses.
Herpesviruses (such as herpes simplex types I and II) are DNA viruses which have the capacity to remain latent in the body for long periods of time. They typically don’t integrate into host DNA but remain in cells (sensory neurons for example) as separate nucleic acid structures, sometimes complexing with host chromosomes.
More than you probably want to know on the subject here.
By contrast, retroviruses are RNA viruses which use reverse transcriptase to integrate into host DNA.
There are a variety of reasons.
HIV infects immune system cells, and is a retrovirus, so it has a significant ability to escape immune system activity. Anti-retroviral drugs suppress HIV replication, but cannot eliminate the virus DNA from infected cells.
Similarly with herpes simplex (herpes) and varicella zoster (chicken pox/shingles) - they specifically infect neurons, and lie dormant until there is an opportunity to reactivate, often due to unrelated immune system changes.
For chronic Hep B, it seems to be due to an incomplete immune response that develops viral surface antigens, but not a core viral antigen response. This may be due to un-developed immune systems (chronic Hep B is often associated with maternal Hep B transmission during or soon after birth), or a suppressed immune system when infection occurred. My chronic Hep B was cured during a drug trial that used a genetically engineered protein to stimulate the missing core antigen response. I got lucky, but I have not seen further developments of the therapy - no-one else in my trial cohort had the same response. I think it likely that the same approach would be trialed with an mRNA vector in future. Hep B can be treated and suppressed with antiviral drugs that are similar to (and sometimes the same as) HIV antiretrovirals.
Fun tangential fact: While reading about shingles a few months ago, I came across the fact that smallpox virus is not related to chickenpox and other herpes viruses.
That’s because the word ‘pox’ is derived from the old english ‘pocc’, meaning blister or pustule. Hence a pocc can be caused by a wide variety of things, not just one family of viruses.
What’s the deal with HPV then? Apparently it was once believed to be like herpes, i.e. you had it forever, but it’s now known that something like 80% of people will clear the infection. But that means 20% won’t. What’s up with that?
It’s not fully understood why some people don’t clear HPV infections while over 90% do.
Immune system variance and even random events in infected cell division have been suggested.
It has also been reported that at least in some cases, infection greatly increases the risk of re-infection with that strain of HPV.
The odds in general strongly favor the vaccinated.
Well now, that’s also somewhat contrary to expectations. I wonder what causes that.