What types of illness would be allowed on a generation ship and why?

In summary, according to the summarizer, it is inevitable that some people will be ill on a generation ship. Some illnesses are allowed, such as viruses, while others, like fungi, are not. Bacteria is in a gray area, while parasites are not allowed at all. The pathogen left is prions, which are not allowed under any circumstances.
  • #1
caters
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With 44000 people for genetic diversity reasons, it is inevitable that some will be ill. Now the types of illness allowed would differ.

Take viruses for instance. A cold virus like this rhinovirus:
hqdefault.jpg

Would be no big deal. It would just cause a cold.

Ebola on the other hand would be a huge deal because of those diagnosed, half of them die. Yes you heard me right, 50% death rate. And with there being a lot of sex going on regularly and the likelihood that someone will touch blood or urine being high, especially in children, this would spread widely and even if just 1 person had Ebola, there would be a massive die off over time. Reproduction rate would start high but as more die, the reproduction rate will drop until it is lower than the 50% death rate(in other words when teens and older comprise less than 50% of the population). Once that happens, the whole population is guaranteed to die off.

So while this might mean needing eggs and sperm of healthy people and artificial wombs as a backup, it doesn't mean that no people should be on it.

In fact, I think the worst viral infections that would be allowed are skin infections that go dormant(like chickenpox) and severe respiratory infections(pneumonia for instance). Any worse and the death rate would be too high, I think. Even the worst viral gastroenteritis wouldn't be immediately life threatening or cause a massive enough die off if transmitted for the entire population to eventually die.

Fungal is another story. A lot of fungal infections and I mean, a lot, are mild. Skin infections, vaginal yeast infections, both of those types of fungal infections are mild. Most severe fungal infections occur in people with weakened immune systems or lung disease or in those fighting another infection like a bacteria or a virus. So death rate from fungi is low, so low that I don't think fungal diseases should be restricted by severity at all. Fungal infections usually spread through direct contact or sex in the case of a vaginal yeast infection. However, sexually transmitted yeast is most likely going to give a male a UTI which can easily be treated with lots of fluids to wash away what is causing the infection. Yeast infections are also the most likely to be resistant to antifungal treatment.

So far we have this on the spectrum:
386RPH6.jpg

Now come the big guns. Bacteria. Just 1 group of bacteria species can cause all these illnesses:
  • Strep Throat
  • Impetigo
  • Scarlet fever(which is common after untreated strep throat)
  • Pneumonia
  • Toxic Shock Syndrome
  • Flesh Eating Disease
And these complications after the infection is over:
  • Acute Rheumatic fever
  • Rheumatic heart disease
  • Post-streptococcal Glomerulonephritis
So yeah, Bacteria would be in the grey area. If 1 bacterial species can cause a mild illness in 1 person but a very severe illness in another, should bacterial illness be allowed at all? I honestly think it should, but only some bacteria. Streptococci would be one of those allowed types of bacteria. Food borne bacteria such as salmonella would likely also be allowed since salmonellosis would most likely result in gastroenteritis. Some subspecies of salmonella can cause typhoid fever or paratyphiod fever though. These are the life-threatening types of salmonella. But like I said, most salmonella would only cause gastroenteritis. In fact lots of different bacteria can cause gastroenteritis.

Parasites are another gray area. You have 2 types of parasites, heleminths, such as tapeworms, and protozoa, such as plasmodium falciparum. Malaria is parasitic but it causes hemolytic anemia and periodic fevers. Plus, it is unlikely that mosquitoes would survive on a generation ship due to lack of stagnant water. Intestinal parasites on the other hand will most likely only cause diarrhea or sometimes, no symptoms at all.

So far we have this on the spectrum:
kH4lRQk.jpg

There is only 1 pathogen left. That is prions. These are not organisms nor are they cellular parasites(viruses are in a sense cellular parasites because they invade cells to cause an infection and can't multiply without the cells), they are simply proteins that are misfolded which cause normal proteins to become misfolded. The only way I could see getting rid of prions before infection is a lot of protease supplements on top of normal digestive enzymes to ensure the proteins are broken down. This would not be ideal because it is quite possible that these proteases would themselves cause intestinal inflammation. So this would be in the red area, absolutely not allowed, not even in 1 person.

So here is the full spectrum:
nVHuGCI.jpg

However, if I were to go through a list of every infectious illness and decide whether or not it is allowed, should I have a death rate limit? Is there a point at which pregnancy rate and more importantly birth rate, can't overcome the death rate from infection assuming an average death rate of 8 per 1000 per year from other causes?

So is there a point at which death rate from infection would cause something like this to happen to the population:
image1.jpg

In other words exponential decay once the birth rate lowers to below the death rate?

Assuming about a fourth of the women are in the fertile window per week and a sex ratio of 1:1, this means with every pairing, there is at most a 25% pregnancy rate per week in the population. But of course, those that didn't get pregnant before would try again and so it would increase to be more than 50% of the women within a month that get pregnant, say something like 80%. Of those that get pregnant say 20% miscarry and 1% end up with a stillbirth. This would mean a 79% birth rate in pregnant women which would mean a 31.6% birth rate in the population overall. And this 31.6% would be every 2 years, except that 2% of breastfeeding women will get pregnant before their periods and the chance of getting pregnant increases with every passing period until after 2 years, when breastfeeding stops, it gets back to the 80% rate. Sort of like a slow but exponential growth.

Main reason for allowing illness? Immune systems in their prime and prevention of these:
  • Autoimmune disease(without illness, it is more likely the immune system will see something harmless as foreign)
  • Allergies(same thing, just not against human tissue)
  • Weak immune system(this would be the worst, this could mean major die off from minor illness)
 

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  • #2
What is the purpose of your post? Are you writing a sci fi story?
 
  • #3
Yes I am but I don't yet know what to name my story or if teens will be allowed to become pregnant or what restrictions would be good for selecting 44000 genetically diverse and healthy people out of 7.6 billion people in the whole world or if an entire world survey with the amount of detail that would be needed is even possible.

This "what is the highest death rate I should allow to prevent the population dying off" question is just 1 of many questions I would be asking myself and probably other people before I actually get started writing it or at least before my second draft of the story. So yes as you can probably tell I am aiming for a realistic sci fi story.
 
  • #4
I think you’re over thinking this in an attempt to make it completely accurate. It would be better to establish some number, work your story around it, and maybe introduce a wildcard that messes with the balance like rescueing someone along the trip or someone impersonated a passenger and brought a dangerous illness aboard.

Some resources to help your story along:
- Saves The Cat by Blake Snyder 3 books on how to write screenplays but would help with plots and strategies.

https://www.amazon.com/gp/product/1932907009/?tag=pfamazon01-20
- Orson Scott Cards book

https://www.amazon.com/gp/product/158297103X/?tag=pfamazon01-20
 
  • #5
Well. How do you plan to select the initial crew?

Just because, you know, nobody will enlist for a mission which includes significantly higher chances of death than already present in the home society.
Given the stated 44k number, the crew should be highly skilled, which also implies a good health care and (usually) low birth rate.

How many generations are you planning for?

Most writers tends to worry about genetic degeneration or such, but that's a long term stuff (and actually easy to avoid). How do you plan to cope with the education? A mere 44k initial crew must be highly educated//specially selected to be able to maintain a ship big enough, however, the right the next generation will be just as 'average' as usual...

Autoimmune diseases, allergy, weak immune system: be careful. There are some people who says that these are linked to the missing sicknesses, but actually more things points to the missing dirt instead... And this difference does matter.
 
  • #6
Rive said:
Well. How do you plan to select the initial crew?

Just because, you know, nobody will enlist for a mission which includes significantly higher chances of death than already present in the home society.
Given the stated 44k number, the crew should be highly skilled, which also implies a good health care and (usually) low birth rate.

How many generations are you planning for?

Most writers tends to worry about genetic degeneration or such, but that's a long term stuff (and actually easy to avoid). How do you plan to cope with the education? A mere 44k initial crew must be highly educated//specially selected to be able to maintain a ship big enough, however, the right the next generation will be just as 'average' as usual...

Autoimmune diseases, allergy, weak immune system: be careful. There are some people who says that these are linked to the missing sicknesses, but actually more things points to the missing dirt instead... And this difference does matter.

Here is how I plan to select the initial crew out of 7.6 billion. First off age restriction. I plan to restrict the ages in the initial crew to 18-80 years. This brings the population down to ##5.5362 * 10^9##

Now were getting somewhere, that is about 2/3 the initial population.

Next up, illness, this is going to be a complicated one to figure out because I would have to add every illness over some death rate(which I do believe the maximum death rate without exponential decay would be a replacement rate, i.e birth rate = death rate), extrapolate it, and subtract that from the population.

Now for fertility. Since the aim is for people to reproduce generation after generation, you would want no sterile couples. Infertile should make up a minority, like maybe 2% or so. 9% of men are infertile and 11% of women are infertile and for couples with infertility it is roughly 1/3 attributed to men, 1/3 attributed to women, and 1/3 attributed to both. Since I am aiming for a 1:1 sex ratio and monogamy(don't know if it should be serial monogamy(1 partner 1 cycle, a different one the next cycle), or lifetime monogamy(staying with 1 partner and only having sex with that 1 partner for life)), I will aim for 1% infertile males and 1% infertile females. So that means that ##2.22528 x 10^8## males and ##2.7816 * 10^8## females would be gone. I can't really find stats on how many people are reproductively sterile though but I found that it is accounted for in infertility statistics as is subfertility. This brings the population down to ##5.062512 * 10^9## Not much but it guarantees that the majority will get pregnant.

Next up, weight, 35.9% of people are overweight or obese and about 19% are underweight. This brings the population down to ##2.779319088 * 10^9##

I don't know what other restrictions I will need though.

As for the number of generations, it would be however many there are in 800 years.I know they say a generation is 31 years but I don't really buy that. When I think of generation I think of how far down someone is on the family tree. So for example, my second cousins would be in the same generation as me as would, well all my cousins without the x times removed. My great great grandfather would be 4 generations behind me, any future children I have will be 1 generation ahead of me. That is what I think of when I hear generation, not some number of years based on the average age of the father and mother of a middle child. According to this family tree definition of a generation, the record number of living generations in a single family is 7. That must have been from a family where teen pregnancy was the first pregnancy for every generation. The oldest person in that family, the great great great great grandmother, is 109 years old or at least was 109 years old in 1989 when the record was given to that family.

As for education, I actually only need average level education because the aliens on it would be doing all the work of maintaining the generation ship. Of course high intelligence is always good.
 
  • #7
Why would you want to bring any viruses or parasites on a generation ship?

If you later decided that you really want a rhinovirus you can copy the RNA sequence from a digital database.

With a human population of 44,000 most rhinoviruses would become extinct after 1 epidemic. You would need to have people segmented into smaller sections so that the virus could fester in one population before getting transmitted to the next. The virus has to mutate before it can spread through the same population. If all 44,000 people are in a single community then immunity will kill off the virus before it mutates sufficiently.
 
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  • #8
stefan r said:
Why would you want to bring any viruses or parasites on a generation ship?

If you later decided that you really want a rhinovirus you can copy the RNA sequence from a digital database.

With a human population of 44,000 most rhinoviruses would become extinct after 1 epidemic. You would need to have people segmented into smaller sections so that the virus could fester in one population before getting transmitted to the next. The virus has to mutate before it can spread through the same population. If all 44,000 people are in a single community then immunity will kill off the virus before it mutates sufficiently.

Its not a matter of why? its more a matter of imperfect screening of pathogens based on our knowledge. Imagine if pathogens could be created as a side part of human breeding. Perhaps that could be a feature of the story where you imagine that a pathogen is created from generations of breeding. We are after all composed of bacterial colonies needed for processing our food.

@stefan r brings up a good point, you could have your populations separated so as to prevent a pathogen from wiping out the ship into separate colonies of people. However that separation allows for a benign pathogen to mutate into one not so benign to the other colonies onboard.
 
  • #9
Since it is a Sci Fi ship it may be useful to reject anyone with a lung deficiency so that if the oxygen supply decreases such as if people need to leave a large section of the ship due to an emergency thus concentrating them into an area that does not have enough oxygen for the entire crew due its size. Also people with immune deficiencies should also be rejected due to their ability to allow a virus to more easily build up inside them and transmit to others.
 

1. What is a generation ship and how does it work?

A generation ship is a hypothetical spacecraft designed to travel long distances through space, carrying a large number of people for many generations. It is intended to be self-sustaining, providing everything needed for human survival, including food, air, and water. The ship relies on advanced technology and a closed ecosystem to maintain the health and well-being of its passengers.

2. How does illness affect a generation ship?

Illness on a generation ship can have a significant impact on its inhabitants. Since the ship is a closed environment, any disease or illness can easily spread among the population. This can lead to a decrease in productivity, potential loss of life, and a strain on the ship's resources. Furthermore, if the illness is not properly treated and contained, it can threaten the survival of the entire population.

3. What are the common health challenges faced on a generation ship?

Some of the common health challenges faced on a generation ship include the risk of infectious diseases, the effects of prolonged exposure to microgravity, and the psychological toll of living in a confined space for an extended period of time. Other challenges may include maintaining a balanced and nutritious diet, managing mental health, and dealing with medical emergencies without access to advanced medical facilities.

4. How do scientists and medical professionals prepare for illness on a generation ship?

To prepare for potential illnesses on a generation ship, scientists and medical professionals conduct extensive research and simulations to anticipate and understand the possible health challenges that may arise. They also develop protocols and procedures for preventing and managing illnesses, such as regular health check-ups, quarantine measures, and emergency response plans. Additionally, they work to create a diverse and resilient population through genetic screening and selection.

5. Can illnesses be completely prevented on a generation ship?

While extensive measures can be taken to prevent and manage illnesses on a generation ship, it is impossible to completely eliminate the risk of disease. The ship's closed environment and limited resources make it vulnerable to outbreaks, and the long duration of the journey increases the likelihood of encountering new and unknown illnesses. However, with careful planning and preparation, the impact of illnesses can be minimized and the survival of the population can be ensured.

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