I want to know if the disease I invented is logical or just a total fiction.

A parasite (parasitic fungus) lives within the human brain. It infects other humans by releasing spores while invoking states of rage within their hosts. This makes it easier to infect other humans as it's similar to a "zombie" virus, if you will, though they're not dead. (I know there isn't any parasitic fungus which can infect humans, but let's say a new species was found or created in this story.)

The peculiarity of this parasite is that it can only infect people who are over 25 years (or thereabouts). Why? Because the brains of the people who are under 25 (on average) haven't reached the fourth age, so the parasite isn't viable. The frontal lobe in particular is the important factor, because to be viable for the parasite it needs to be fully developed.

There are five brain ages:

  • 1st age: during pregnancy. The first neurons are formed from the 28th day of pregnancy in the embryo.
  • 2nd age: from birth to 12 years.
  • 3rd age: from 12 to 25 years old. (The regions in the frontal lobe are getting fully developed in the mid twenties.)
  • 4th age: from 25 to 65 years old.
  • 5th age: from 65 years old to ...

Oh, and if a vaccine could be found, in what way will it be the most effective?

So, do you think this parasite is possible or completely unrealistic? If you have any suggestions or ideas to make it more realistic, I'll gladly read them.

  • 4
    $\begingroup$ Seems like you want a parasite that can only be triggered by or harbored within a mature frontal lobe, but whose effect is to alter the chemistry of the nearby midbrain. Perhaps, in one stage of their life cycle, they colonize the mature frontal lobe, but migrate regularly to the midbrain for reproduction, then return. Lots of weird possibilities. Beware attributing purpose to wee parasites, unless you are actually stating that they are sentient. $\endgroup$
    – user535733
    Dec 28, 2018 at 4:48
  • $\begingroup$ @erubisu, I just did a massive edit on your question. If you don't like my changes, please go ahead and edit the question again or do a "rollback" to change everything to how it was before I touched it. I am hoping it is useful to you (and my answer too!). $\endgroup$
    – Cyn
    Dec 28, 2018 at 7:42
  • $\begingroup$ It sort of is like the flare virus from the maze runner series, as init invokes rage, is a virus, and makes the victim go crazy and zombie like $\endgroup$ Dec 28, 2018 at 9:35
  • $\begingroup$ it affects the brain also $\endgroup$ Dec 28, 2018 at 10:03

3 Answers 3


A plausible explanation could be that a fully-developed frontal lobe is required to breed the virus to the point where the brain is overtaken.

Instead of drawing a hard line and saying that it can only infect people at 25 or over, it'd be much more natural to say that it's incredibly rare to be infected below that age range.

A vaccine doesn't sound doable with modern medicine, since your virus presumably takes control of the person's entire body, including motor functions, choice, etc. Not only would this make them not want to take a vaccine, but the only real vaccine that could exist would be to full-on cut out the frontal lobe before the virus expands too far.

So you know, it is /sorta/ possible for a human to live without a frontal lobe, but that kind of virus probably shouldn't be out there.

Hope this helped!

  • $\begingroup$ Thanks for the answer, i agree with the fact that it's really rare to be infected below 25 instead of drawing that hard line. And yeah, i thought about the same thing for the plausible explanation. $\endgroup$
    – Erubisu
    Dec 28, 2018 at 14:22

The parasite lies dorment in wisdom teeth.

Wisdom teeth usually emerge sometime between the ages of 17 and 25. They have that name because their emergence generally coincides with maturation, with adulthood.

Wisdom teeth are unique because there is only one set of them. For all the other teeth, there are baby teeth (which fall out between the ages of 4 and 13, depending on the placement of the teeth and with some individual variation) and permanent teeth. None of the other teeth work for the parasites because the baby teeth fall out too soon and the permanent teeth are buried under the baby teeth for the first few years.

Most people are infected as children but the parasite doesn't cause any symptoms when in the dental pulp. It is not until the wisdom teeth emerge that the parasite is mature and able to migrate to the brain (up the back of the throat to the nasal cavity then, with some burrowing, it finally reaches the brain).

There is no vaccine, but early removal of wisdom teeth (still inside the gums) is a pretty good preventative.

Is this scenario realistic? No, not particularly. But it has the right timeline and might help you sell your storyline. I hope it is useful to you.

  • 1
    $\begingroup$ Thanks for your answer, you may have done a massive edit but it's quite nice. I will keep in mind that idea. And yeah, i know that my parasite or your scenario isn't realistic since it doesn't exist, but as you say, i want the story to have a good timeline and not being supernatural, that's why i need some science to back up/explain the disease. $\endgroup$
    – Erubisu
    Dec 28, 2018 at 14:30

Persons 25 and younger were (inadvertently) vaccinated against the brain fungus.

New vaccines are periodically rolled out. For example the chickenpox (varicella) vaccine came out in 2005 and subsequently in countries where kids get vaccinated, kids were vaccinated with it.

In addition to immunity from chicken pox (or whatever the target is of the vaccine in your story), a side effect of that vaccine is that it also conferred immunity to a fungal contaminant in its manufacture. The fungal contaminant is related to the dementing brain fungus. Persons who received that vaccine as children are therefore immune to the brain fungus.

Upside - you have a hard date between which people are immune and not immune. You do not have to posit a hard difference between the brains of 23 year olds and 27 year olds.

Downside - unvaccinated infants are not immune. Persons in 3d world countries that do not use the vaccine in question would not be immune. Antivaxers would not be immune.

  • $\begingroup$ Thanks for the answer, i didn't thought about that aspect for a vaccine. And yeah, for age it's approximatively around 25. $\endgroup$
    – Erubisu
    Dec 29, 2018 at 10:38

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .