A Plague that Causes Death in All Post-Plague Children

Question

The backstory of the world in the story I am writing tells of a deadly plague that significantly depopulated all of humanity. Years later, as the survivors began to recover post-plague they noticed that all children born after this event would go on to die suddenly, shortly before the onset of puberty. This was later discovered to be an after effect of the plague which created a new disease that passes from parent to unborn child in all the offspring born in this new generation.

With these details in mind, my question is two-folds. First what types of infectious virus should I research to develop a disease that affect the unborn of the previously infected populace (Kinda like of Zika). Second is it plausible for a disease like this to have such a long incubation/latent period followed by a rapid progression that begins around puberty with a 100% mortality rate?

Answer 1

A virus cause genetic mutation in the parents.

A virus-induced mutation in the germ plasm of the parents. It does not alter their own bodies, but it does edit the DNA in the eggs or testes (thus in the sperm).

This mutation is dominant, and manifests in 100% of the offspring of post-plague parents.

It affects the function of the Pituitary gland in their offspring, making it release a malformed version of gonadotropins, which then proceed to wreak havoc on the poor kids. As the activation of these hormones is the exact thing that normally triggers the onset of puberty, it will strike with clockwork accuracy in its victims.

Sadly, because it it not a disease but an inherited trait, it will be incurable. Possibly symptomatically treatable, but incurable.

As asked in questions: Some scholarly comment and examples on viral alteration of reproductive DNA.
https://www.biorxiv.org/content/10.1101/2020.06.04.135657v1.full shows proof that human DNA has been "infiltrated" repeatedly, somewhere in our history.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6159993/ shows how the Zika virus causes Teratogenic effects by altering the DNA in semen.(actually in the seminiferous cells)

Usually viral teratogenic effects occur only directly, by the virus infecting the embryo as the mother gets the virus during early pregnancy. Even more often the mutating effect is only due to a chemical/hormonal imbalance effect during embryo development. Effectively the toxins from being ill "poisoning" the child within the sick mother. But sometimes, the virus can infect and alter cells without killing them. And if these cells happen to be the sperm-producing organs of the male, or the eggs in the female, the results can be a permanent editing of all subsequent offspring.

Answer 2

It's HIV - but your society doesn't have the treatments we do.

So with current medical knowledge HIV positive and uninfected people have the same life expectancy, and the odds of passing mother to child is 1 in 50, but without that knowledge, the disease does what you want.

The plague that kills the children is literally AIDS developing from a HIV infection. HIV could've been spread among the parents via blood transfusions used in the treatment of the (possibly even unrelated) first plague, spread through your societies tattooing tradition, or it could've been spread through the your societies underground drug scene, or perhaps some adult events that are best left to the reader's imagination.

Not all children catch HIV from their HIV positive mothers - the odds are actually only 1 in 4 for birth alone. But by encouraging breastfeeding that could go up to nearly 100%.

In a world without modern medicine; a child born with HIV has a 20% chance of sick by age 1 and death by age 4 (which may slip under the radar if your infant mortality is shockingly bad already, or blamed on some other thing), but the rest will start to show symptoms around age 2-3, with a life expectancy of about 10 years after diagnosis, getting full blown AIDS just before puberty, and dying at about the time you need.

A very small percentage (<10%) of humans are immune to HIV, so your society will have survivors if it becomes a pandemic.

Answer 3

Maternal -fetal transmission.

This was in the news most recently as regards the Zika virus, and of course a woman infected with HIV can pass along that infection to her unborn infant. Worldwide, hepatitis B is far and away the main infectious agent transmitted from mother to fetus.

Hepatitis B Virus Infection during Pregnancy: Transmission and Prevention

The risk of maternal-infant transmission is related to the HBV replicative status of the mother which correlates with the presence of HBeAg as 90% of HBeAg-positive mothers transmit HBV infection to their offspring compared to only 10%–20% of HBeAg-negative mothers.9 The high frequency of perinatal transmission in endemic areas is probably related to the high prevalence of positive HBeAg in women of reproductive age in these countries. Studies have shown that the rate of HBeAg seroconversion during the first 20 years of life is relatively slow, leaving many women of childbearing age who have contracted HBV infection in their early childhood still highly infectious to their infants.10

The importance of perinatal transmission becomes paramount, because follow-up data on persons infected as infants or young children demonstrate that about 25% of persons who have chronic infection die prematurely from cirrhosis and liver cancer; the majority of whom are asymptomatic until onset of end-stage liver disease. At the same time, individuals who have chronic infection serve as the major reservoir for continued HBV transmission.11

Your "plague" survivors are actually carriers (plague here in quotes because this is some unspecified viral scourge, not bubonic plague!). Their unborn children contract plague in utero and suddenly die later in life like babies who suddenly die of liver failure from unsuspected hepatitis B. Some babies with hepatitis B grow up and live to reproductive age and conceive and infect their own babies with hepatitis B - maternal fetal tranmission is the main mode of transmission in some places.

This might be the end result of your plague too - a population of chronic carriers, who are the persons who lived to reproduce in the context of the plague. This is how evolution works.

Answer 4

Something akin to the sickle cell disease, which grants protection from malaria to those who are heterozygote for the defective version of the gene, while causes the onset of the disease in those who are homozygote.

The adults who survived the virus where only those bringing a recessive gene for a genetic disease being lethal in pubers, because this gives them resistance to the virus. When they procreated they necessarily had a progeny being homozygote for that gene, thus as soon as they reached puberty they started to develop the disease and die.

Answer 5

As a possible twist on @PcMan's answer, rather than have the virus cause the genetic changes (though that's possible), instead have it so that the virus killed off everyone other than carriers of this mutation.

https://en.wikipedia.org/wiki/Sickle_cell_disease is a good example of a genetic disease that gives the carrier a significant advantage against a disease (malaria), at the cost of causing sickle cell disease if you get both copies of the gene.

Normally, then, sickle cell carriers are a minority in a population. But where malaria is common, they become a larger proportion of the population because people without it die a lot more often.

If a very contagious and deadly novel virus formed, with a lengthy asymptomatic contagious period, for which there was no vaccine, then it could easily wipe out everyone who lacked immunity to it within a year.

If immunity meant that all children would get two copies of a gene that would eventually kill them, then all children would be doomed.

The mechanism to kick in at puberty probably also needs some attention, and again there's a good existing example of a genetic disease which needs copies from both parents in order to trigger, but which triggers at puberty: https://en.wikipedia.org/wiki/G%C3%BCevedoce.