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Suppose there was a disease that caused accelerated healing in the host body during incubation. Once symptoms appeared, the initial advantage was replaced by the real, negative purpose.

How realistic would such a disease be? Are there any functions for which this behavior would be particularly well-suited?

One idea I have is the disease is based on plant spores that grow inside the host, accelerating healing, and eventually sprout into plants that use the host as fodder.

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  • $\begingroup$ Is it an artificial disease or naturally occurring? $\endgroup$ – JDSweetBeat Apr 9 '15 at 15:31
  • $\begingroup$ @DustinJackson Answers to either variety are acceptable, but I'm most interested in a natural disease. $\endgroup$ – Frostfyre Apr 9 '15 at 15:56
  • $\begingroup$ smithsonianmag.com/innovation/… $\endgroup$ – apaul Apr 9 '15 at 17:16
  • $\begingroup$ Your description makes me think of mania, a real-life mental disorder in which victims feel unusually and dangerously happy and energetic. One of the main risks is that sufferers have greatly reduced inhibitions and are much more likely to make dangerous decisions. Unfortunately, people suffering from mania often feel too self-confident as a result of the illness to be willing to seek help, causing the condition to worsen. It's not caused by a pathological agent, but it sounds like something that might be relevant to your world nonetheless. $\endgroup$ – Kevin Apr 9 '15 at 20:53
  • $\begingroup$ I did read up on a certain strain of flu first attacking some specific bacterial disease, effectively healing the patient from it, before switching to native cells of the infected. The evolutionary advantage is clear: destroy the competing species, have the host all for yourself. I'd need to find where I read it. $\endgroup$ – SF. Apr 10 '15 at 11:09
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This would be unlikely, but not impossible. The biggest challenge is how to accelerate healing.

I envision this disease as being very species-specific, and it will need to have at least two different phases. Perhaps a parasite would be an ideal candidate, rather than a bacteria or virus.

First, let's talk about how healing works, and then we can talk about an evolutionary pathway for the disease.

Healing

Healing in humans is very complicated. The "simplest" healing is repair to a cut or scratch. But their is also inflammation repair, fighting diseases, replacing necrotic tissue, etc. Our disease agent would have to either co-opt this process, or perform its own form of healing. Since humans (and mammals in general) have been evolving and perfecting our healing process for many hundreds of thousands of years, I'm leaning towards a custom healing process.

For example, our disease agent may be able to reconfigure arbitrary cells into stem cells, and then use those cells to patch damage. Our disease agent may also come with a slew of antibacterial and antiviral compounds, which is releases into the body. Other healing methods are possible.

Life Cycle

The problem that we have is we need a disease that has two distinct phases: a healing phase, and a hurting phase. Normal bacteria and viruses are generally not complicated enough to support this distinction. Parasites, on the other hand, are.

I envision the first phase of our disease agent as being a slow reproductive journey to a "critical mass" of disease agents. Then, after it reaches critical mass, it switches to an attack mode to aid distribution of the disease agent.

But how could something like that come about?

Evolution

I envision an evolutionary pathway as follows:

First, we have a parasite that, for its own protection, naturally evolves antibiotic and antiviral compounds that it releases into its host. This is advantageous because, not only does it protect the parasite, it also benefits the host, which makes the parasites home that much more resilient.

However, this poses a problem for the parasite, as the healthy host tries to fight it off, and it is unable to spread as easily. The parasite evolves to include an "attack" phase, where it cuts off its antibiotics/antivirals and initiates an inflammation response that causes the body to attack itself. This allows a rampant breed cycle that causes the parasite to shoot up in numbers, and when other humans try to help our victim, are spread via touch or water contamination.

Over time, the parasite perfects the healing routine. This is an evolutionary advantage, because a healthy host gives the parasite mobility, and limits any competition for the host's resources when the parasite goes "critical".


There may be other ways to explain this type of a disease, but this seems to me like the path of least resistance.

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  • $\begingroup$ Good information and a good analysis. Thanks. $\endgroup$ – Frostfyre Apr 9 '15 at 15:58
  • $\begingroup$ You do not necessarily need any shift in modes from healing to hurting - there are many examples of our immune system getting over-excited and killing us (or at least making us very ill). Whatever mechanism is improved by the infection eventually gets over-stimulated, which triggers something akin to a cytokine storm once it hits a certain tipping point, causing a positive feedback loop resulting in the victim being killed by their own boosted immune system. Both phases covered with a single mechanism. $\endgroup$ – pluckedkiwi Apr 9 '15 at 18:08
  • $\begingroup$ I would disagree with you on your evolutionary timeline. Firstly, I would not call it a parasite, since it DOES confer advantages to the host, thus it is a mutualistic relationship. As time goes on, the entity would adapt to the host to a point where it would be able to stay there indefinitely (and not harm it), once this occurs, natural selection would select for host with the entity. Eventually all host will have the entity in them, and it would be part of the host. $\endgroup$ – Aron Apr 10 '15 at 3:44
  • $\begingroup$ @Aron Not necessarily. If the "critical" phase provides a transmission advantage, then evolution will continue to select for it. And, for clarification, by parasite, I mean something like a traditional macroparasite. $\endgroup$ – Nick2253 Apr 13 '15 at 14:39
  • $\begingroup$ @Nick2253 There are plenty of endosymbiosis. There is no reason to stop an endosymbiont from being...erm...macro. As for the "critical" phase, that would eventually extend to the entire life of the host, since survival of the host is required for the survival of the symbiont (the most successful infectious diseases don't kill host, like the flu). $\endgroup$ – Aron Apr 13 '15 at 14:49
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What about a disease that speeds up your metabolism and the literal rate at which your cells grow and die? Maybe at a 5:1 or 10:1 ratio greater than normal?

So you would get accelerated healing as a side effect, but you'd need to eat a ton (possibly causing malnutrition after a while) and you'd rapidly age into becoming elderly, along with all the fun diseases you get from that (organs growing weaker, cancers, heart failure, etc). All of which are magnified by the fact that you can't get enough food, so generally you're dead within 3-5 years.

One side effect I don't have a great solution for is presumably you'd also need more oxygen, but I could be wrong about that.

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Might be feasible as an auto-immune disease. Virus infections and auto-immune diseases are linked together. The virus starts of as semi-benign virus that stimulates the body's healing functions (I'm less sure on this part, genetic engineering of virus's that can cause healing of the heart to prevent heart failure is a valid field of research in the UK, but that is very specifically engineered).

Here : http://www.ncbi.nlm.nih.gov/pubmed/14596882

I hypothesize that human chronic autoimmune diseases are based on infection of autoreactive B lymphocytes by Epstein-Barr virus (EBV), in the following proposed scenario. During primary infection, autoreactive B cells are infected by EBV, proliferate and become latently infected memory B cells, which are resistant to the apoptosis that occurs during normal B-cell homeostasis because they express virus-encoded anti-apoptotic molecules. Genetic susceptibility to the effects of B-cell infection by EBV leads to an increased number of latently infected autoreactive memory B cells, which lodge in organs where their target antigen is expressed, and act there as antigen-presenting cells. When CD4(+) T cells that recognize antigens within the target organ are activated in lymphoid organs by cross-reactivity with infectious agents, they migrate to the target organ but fail to undergo activation-induced apoptosis because they receive a co-stimulatory survival signal from the infected B cells. The autoreactive T cells proliferate and produce cytokines, which recruit other inflammatory cells, with resultant target organ damage and chronic autoimmune disease.

Assuming there is some truth behind the above hypothesis, then it is completely realistic that an auto-immune disease can be triggered by what was once a benign virus. It gives a period of healing / benign effects, before it goes and infects the B lymphocytes mentioned above...this triggers an auto-immune disease which quickly switches it from a benign virus to a system wide fight for survival.

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One potential approach is to start from the assumption that the human body is continuously held in a miraculous balance. Accordingly, our systems are designed not to disrupt that balance except for extreme situations. Fever is an excellent example. We don't mess with the balance of homeostasis until our immune system decides it really can't do anything without breaking that balance.

It would be reasonable for an organism to come in and begin slyly telling the system that it can actually go a little beyond the self-imposed limits on healing rate. The body thus heals itself faster, and feel pretty good about it.

However, the entire time it is being walked off of its balanced state by the organism. Finally, when the body is markedly off balance regarding healing, the organism shifts modes to fully infect the host. If the host had been healthy, the body would have repelled its attacks without effort. However, now that its healing mechanisms have driven some of its subsystems off balance, they're not in a condition to repel the organism.

I seem similarities between this and some drugs which make you feel bulletproof, because your body is no longer trying to hold itself to such a rigorous balance. However, long term usage leads to tremendous health problems as being off balance for that long takes its toll.

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Something like a cancer might fit this.
In the beginning of the infection the cells replicate very quickly and cause healing. But there's a geometric progression, where the cells are reproducing to quickly, and the infection with them. After a while the body begins to be overwhelmed with tissue, and organ damage begins. All of this is still stage 1.
When the disease has replicated itself enough, it causes the cells to rupture, and becomes a hemorrhagic pathogen, like Ebola.

Instead of being a virus, it could also be a spore that enters a cell, and reproduces when the cells divide. When the spore matures is bursts the cell and heads toward the surface. When it reaches an exit from the body (mouth, nose, eyes, ears, wounds, etc.) comes in contact with oxygen and then it releases new spores into the atmosphere.

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The disease could have up to 3 stages, a 'healing' stage, a 'dormant' stage, and an agressive 'attack' stage.

The healing stage could be as simple as the bacteria producing antibiotics or acting like a white blood cell and destroying other pathogens.

Once there is a critical mass of the pathogen, it would go into a 'dormant' phase, where it reproduced, but produced no symptons. The host would return to normal, without any benificial or negative side effects.

Once it reaches a secondary critical mass, it could go into an insane 'attack mode', suddenly producing toxins and attacking cells.

The dormant and attack stages aren't really neccasary - the disease could kill the host through sheer reproduction - the host would die simply because there is more disease than host.

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