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>Ebola is under huge selection pressure to slow down the disease progression in humans. We could see a strain arise that takes a month to kill you where you are

>Ebola is under huge selection pressure to slow down the disease progression in humans. We could see a strain arise that takes a month to kill you where you are asymptotically infectious for a couple of weeks. The virus doesn't gave a goal, to kill the patient. The death of the host is just an unfortunate side effect that really harms the spread of the virus. The really successful viruses have mutated to a form where they don't kill the host, don't make you sick enough to stay in bed, and just make you go to work and cough and sneeze all over everyone at the office.

danieltillett 12y ago
This may all be true, but it does not say anything useful about Ebola and what the selection pressure it is under. At the moment the speed of disease progression to death is so fast that it is slowing the spread of Ebola. If the Ebola took longer to kill it would infect more people. The problem with Ebola is its mechanism of transmission is quite closely linked to the reason it is lethal (large virus production and body fluid leakage). It would take a very large leap in genome space (mutations) to turn Ebola into a virus that is efficiently transmitted, but causes limited symptoms like a Rhinovirus. It is not a large jump in genome space for it to just become slower in progression.
- robomartin 12y ago
  Perhaps the problem is your choice of words. Saying "selection pressure" implies intent, determination, a collective mission, if you will. Evolution has none of those drivers. It has no objectives. It sets no goals. And it certainly does not operate in some collective purpose driven form within a population. It's random mutations that either survive the environmental contex within which they exist, or they don't. In this case the fact that more people are infected does not mean that we are at the doorstep of a "super-ebola" mutation any time soon. It could take ONE mutation or 100 MILLION YEARS of intense mutations to arrive at "super-ebola". Nobody knows. The virus certainly isn't under any "selection pressure" to do a darn thing. It could become perfectly benign in six months just as much as it could become horrifically good at killing us by the millions.
  - lotsofmangos 12y ago
    Selection pressure is the term used widely in evolutionary biology. If you can't get past that choice of words, you wouldn't be able to get anywhere in actually studying the subject, as that choice of words is used throughout. http://scholar.google.co.uk/scholar?q=selection+pressure+evolution http://scholar.google.co.uk/scholar?q=selection+pressure+evo...
  - lindenr 12y ago
    You said: "Saying "selection pressure" implies intent, determination, a collective mission, if you will. Evolution has none of those drivers. It has no objectives. It sets no goals. And it certainly does not operate in some collective purpose driven form within a population." danieltillett said: "At the moment the speed of disease progression to death is so fast that it is slowing the spread of Ebola. If the Ebola took longer to kill it would infect more people." This seems like a true statement and in line with your own opinion; I can't quite see what you are objecting to.
    - robomartin 12y ago
      The death of the infected isn't necessarily the end of the virus. It looks like a police officer inspecting the home of the guy who just died in Texas has now contracted ebola. As I understand it he inspected the home days after the patient had been in isolation at the hospital. Apparently there was vomit, fecal matter, blood and who knows what else in there. Why he went in there without protective gear is incomprehensible to me. The point is that death isn't the end of the virus, it's the end of the host. That's why they are cremating the guy who just died.
  - danieltillett 12y ago
    I guess I could be accused of using technical language with an audience that does not have an biology background. "Selection pressure" means something specific in biology and I used it in that manner. To put what I said in layman’s terms an Ebola viral strain that has by chance a mutation that results in slower disease progression will have more opportunities to infect people than one that kills people faster. If out of the trillion and trillions of new Ebola viral particles being created every second in west Africa one viral particle were to be randomly created that happened to kill people slower, then anyone infected with this new strain would be more likely to live longer than if they had been infected with an original virus particle. This person would then have a greater chance to infect new people and so on. Such a strain would be more contagious, and depending on the exact properties of the strain it may be able to spread even in western countries. I am not saying that this is likely (nobody know), but I would prefer we stop generating all those trillions of random Ebola viral particles and so end this rather dangerous experiment.
- wobbleblob 12y ago
  I gave this some thought, and it occurred to me that smallpox, even after co-evolving with humans for at least 10,000 years, still had a mortality rate comparable to Ebola today, a similar incubation period, and a similar amount of time before the patient was incapacitated. edit: It seems that this wasn't accurate. From wikipedia: >In the United States and South Africa a much milder form of smallpox, variola minor, was recognized just before the close of the 19th century. By the mid-20th century variola minor occurred along with variola major, in varying proportions, in many parts of Africa. Patients with variola minor experience only a mild systemic illness, are often ambulant throughout the course of the disease, and are therefore able to more easily spread disease. Infection with v. minor induces immunity against the more deadly variola major form. Thus as v. minor spread all over the USA, into Canada, the South American countries and Great Britain it became the dominant form of smallpox, further reducing mortality rates. https://en.wikipedia.org/wiki/Smallpox#Other_history https://en.wikipedia.org/wiki/Smallpox#Other_history
  - danieltillett 12y ago
    In regards smallpox there were multiple strains circulating at any point in time and some were more deadly than others. Which ones spread at any point in time depended on both chance and the particular selection conditions in the population. In populations with high levels of immunity (either natural or acquired) the more mild strains tended to spread, while in populations with low levels of immunity the more lethal strains would tend to spread (lot of complicated reasons for this). Your general idea is correct though. Just because a disease has been in a population for a long time does not means that it is harmless, not are all new diseases dangerous.

danieltillett 12y ago

This may all be true, but it does not say anything useful about Ebola and what the selection pressure it is under. At the moment the speed of disease progression to death is so fast that it is slowing the spread of Ebola. If the Ebola took longer to kill it would infect more people. The problem with Ebola is its mechanism of transmission is quite closely linked to the reason it is lethal (large virus production and body fluid leakage). It would take a very large leap in genome space (mutations) to turn Ebola into a virus that is efficiently transmitted, but causes limited symptoms like a Rhinovirus. It is not a large jump in genome space for it to just become slower in progression.

robomartin 12y ago
Perhaps the problem is your choice of words. Saying "selection pressure" implies intent, determination, a collective mission, if you will. Evolution has none of those drivers. It has no objectives. It sets no goals. And it certainly does not operate in some collective purpose driven form within a population. It's random mutations that either survive the environmental contex within which they exist, or they don't. In this case the fact that more people are infected does not mean that we are at the doorstep of a "super-ebola" mutation any time soon. It could take ONE mutation or 100 MILLION YEARS of intense mutations to arrive at "super-ebola". Nobody knows. The virus certainly isn't under any "selection pressure" to do a darn thing. It could become perfectly benign in six months just as much as it could become horrifically good at killing us by the millions.
- lotsofmangos 12y ago
  Selection pressure is the term used widely in evolutionary biology. If you can't get past that choice of words, you wouldn't be able to get anywhere in actually studying the subject, as that choice of words is used throughout. http://scholar.google.co.uk/scholar?q=selection+pressure+evolution http://scholar.google.co.uk/scholar?q=selection+pressure+evo...
- lindenr 12y ago
  You said: "Saying "selection pressure" implies intent, determination, a collective mission, if you will. Evolution has none of those drivers. It has no objectives. It sets no goals. And it certainly does not operate in some collective purpose driven form within a population." danieltillett said: "At the moment the speed of disease progression to death is so fast that it is slowing the spread of Ebola. If the Ebola took longer to kill it would infect more people." This seems like a true statement and in line with your own opinion; I can't quite see what you are objecting to.
  - robomartin 12y ago
    The death of the infected isn't necessarily the end of the virus. It looks like a police officer inspecting the home of the guy who just died in Texas has now contracted ebola. As I understand it he inspected the home days after the patient had been in isolation at the hospital. Apparently there was vomit, fecal matter, blood and who knows what else in there. Why he went in there without protective gear is incomprehensible to me. The point is that death isn't the end of the virus, it's the end of the host. That's why they are cremating the guy who just died.
- danieltillett 12y ago
  I guess I could be accused of using technical language with an audience that does not have an biology background. "Selection pressure" means something specific in biology and I used it in that manner. To put what I said in layman’s terms an Ebola viral strain that has by chance a mutation that results in slower disease progression will have more opportunities to infect people than one that kills people faster. If out of the trillion and trillions of new Ebola viral particles being created every second in west Africa one viral particle were to be randomly created that happened to kill people slower, then anyone infected with this new strain would be more likely to live longer than if they had been infected with an original virus particle. This person would then have a greater chance to infect new people and so on. Such a strain would be more contagious, and depending on the exact properties of the strain it may be able to spread even in western countries. I am not saying that this is likely (nobody know), but I would prefer we stop generating all those trillions of random Ebola viral particles and so end this rather dangerous experiment.
wobbleblob 12y ago
I gave this some thought, and it occurred to me that smallpox, even after co-evolving with humans for at least 10,000 years, still had a mortality rate comparable to Ebola today, a similar incubation period, and a similar amount of time before the patient was incapacitated. edit: It seems that this wasn't accurate. From wikipedia: >In the United States and South Africa a much milder form of smallpox, variola minor, was recognized just before the close of the 19th century. By the mid-20th century variola minor occurred along with variola major, in varying proportions, in many parts of Africa. Patients with variola minor experience only a mild systemic illness, are often ambulant throughout the course of the disease, and are therefore able to more easily spread disease. Infection with v. minor induces immunity against the more deadly variola major form. Thus as v. minor spread all over the USA, into Canada, the South American countries and Great Britain it became the dominant form of smallpox, further reducing mortality rates. https://en.wikipedia.org/wiki/Smallpox#Other_history https://en.wikipedia.org/wiki/Smallpox#Other_history
- danieltillett 12y ago
  In regards smallpox there were multiple strains circulating at any point in time and some were more deadly than others. Which ones spread at any point in time depended on both chance and the particular selection conditions in the population. In populations with high levels of immunity (either natural or acquired) the more mild strains tended to spread, while in populations with low levels of immunity the more lethal strains would tend to spread (lot of complicated reasons for this). Your general idea is correct though. Just because a disease has been in a population for a long time does not means that it is harmless, not are all new diseases dangerous.