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Mutated virus, resistant strains

Matteo Martini

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I keep reading news about mutated strain on virues, which are resistant to anti-biotics:

Gene mutation leads to super-virulent strain of TB, finds new study
http://www.berkeley.edu/news/media/releases/2003/12/08_mutation.shtml

The evolution of the virus says it is getting close to getting ready to do us a lot of harm.
http://www.msnbc.msn.com/id/22451442/

http://timesofindia.indiatimes.com/...nfecting_HIV_in_India/articleshow/2650882.cms
India must prepare its defences immediately. If this XDR-TB strain mixes with HIV, the combination is explosive as it causes 100% mortality

http://news.scotsman.com/education/ALTERNATIVE-TAKE.3628838.jp
This assertion is based upon the facts that the eventual human-to-human killer virus that will emerge will be a new strain, due to the fact that viruses constantly mutate and that, owing to the initial incubation period for bird flu to show its ugly face, the virus will have spread like wildfire across the world through millions travelling internationally on a daily basis.

Is it possible that, due to natural evolution, virueses which have been defeated long time ago, come back with hew potentially much more dangerous strains?

After all, is not is what all evolution is about, with the difference that viruses can evolute much more quickly, due to their shorter life?
 
All viruses are resistant to antibiotics, which work against bacteria. Tuberculosis is caused by a bacterium, and yes there are tuberculosis bacteria that have evolved to become resistant to most of the antibiotics used against them. This is true of other bacterial diseases as well.

The issue with birdflu is a bit different. Viruses are generally not considered to be alive, which is why antibiotics don't work against them. Viral diseases are usually more difficult to cure, which is why we still don't have cures against the common cold, the flu or AIDS. People can be vaccinated against viruses, so it is possible to prevent it, but many evolve so fast that there are many diffferent varieties and you can't be effectively vaccinated against them all. It is possible that a birdflu virus evolves in such a way that it can be transmitted from one human to the other instead of just from bird to human. If that happens we may be facing a global flu pandemic, because it is a pretty problematic flu virus.

There is a bit of hope however: viruses generally evolve to be gradually less deadly. This is because a virus that kills a person too quickly has little chance of spreading, while a virus that hurts people only a little will spread much quicker; people with a non-serious cold will continue to visit other people and infect them.
 
Matteo Martini said:
Is it possible that, due to natural evolution, virueses which have been defeated long time ago, come back with new potentially much more dangerous strains?
Click to expand...
I'd be hesitant to use the word "defeated" in this context except to refer to a virus which has become extinct.

The relationship between pathogen and host is complex and dynamic. There is a tendency to focus on genetically determined properties of the pathogen, but the susceptibility of a particular population to a particular pathogen is strongly influenced by patterns of pre-existing immunity in that population, and other factors as well -- genetic, environmental, behavioral. For example, the epidemiological history of measles exhibits a cyclic nature despite the fact that mutation in the measles virus occurs at such a low rate as to be virtually negligible. Some pathogens rely on mutation to evade host defenses; others simply wait for host populations to breed up fresh batches of susceptibles. Though the H5N1 virus remains a threat to us, there isn't any reason to suppose that humans are a particularly attractive target. The virus is doing just fine in avian populations, and rapid population turnover is only one of the qualities birds have to offer as hosts. But diseases do cross species boundaries, and pathogens have been engaged in running battles with human immune systems since the dawn of time -- and while it's true that they are capable of much more rapid mutation that are humans themselves, the human immune system includes components which mutate even more rapidly (it's called "somatic hypermutation").

The fortunes swing back and forth. Evidence from mitochondrial DNA suggests a bottleneck in the global human population around 70k years ago, and an alternative to the Toba catastrophe theory explaining this is that this represents the impact of a particularly virulent pathogen, perhaps an influenza virus. Even before the advent of antibiotics, antivirals, and vaccines, there may have been pathogens that were defeated utterly (and became extinct), and it seems unlikely that in the entire history of the planet there have not also been some which, lacking the foresight to which Earthborn has alluded, pressed their victory so far that they also ended up defeated utterly, and became extinct, by virtue of having brought this same fate upon the hosts upon whom their existence depended.

Conversely, the very success of the artificial defenses we have devised against these pathogens creates what might be thought of as a new type of vulnerability: any pathogen capable of evading these artificial defenses is potentially more dangerous on that basis alone.
 
I read a book a while ago about the influenza horror in 1918 that was fascinating because it treated the whole topic in perspective (i.e. germ theory was relatively new) and featured the heroics of the medical practitioners and researchers as they scrambled to figure out what was going on. A quick google led me to Crosby "Amerca's Forgotten Pandemic: The Influenza of 1918" but it could have been another book. Wonder if any of you have read that, and what you thought.
 
Matteo Martini,

This TB strain is 100% fatal? Or just with HIV and the disease?
 
INRM said:
Matteo Martini,

This TB strain is 100% fatal? Or just with HIV and the disease?
Click to expand...

Honestly, I do not know.
This discussion has gone into a detail I am not able to deal with, as unfortunately, I am not a biologist, and I only have studied biology in high school
 
Sorry if I replied very late to this thread, I have read the replies by EarthBorn and Dynamics and I realized that I have no specific competence on the matter.
Before even starting, I excuse me for the non-technical way I am trying to explain my point-of-ciew and the obvious errors I will unavoidably make.
I tried to do some basic research on the matter, but I higly doubt I can come out with appropriate answers to their comments in a few days` time.
Therefore, I have to rewrite my point in more simple terms.
Basically, during the last 100 years, the average life expectancy of man has grown from about 50 years old to about 75 y.o. (with women living about 5 years more than men, dunno why), at least in developed countries.
This is due to many factors: better sanitation, vaccinations, food every day and cures for basic illnesses.
Now, can we consider this result as a permanent "victory"?
If, like all organisms evolve, also viruses and bacteria that have been found curable in the last 100 years are evolving, can not we expect a come-back of different variation of the bacteria/viruses in forms which will be not curable, and will need other research to find appropriate cures?
Can we say that we have find the way to cure a virus/illnesses caused by it once for all?
Or can not we expect that new viruses like HIV and Ebola will come out, or new evolved strains of old viruses/bacteria, and that the battle will start all the time over and over again?
Also, since illnesses were one of the factors that drove evolution in human to make us more resistant (when ill people died and could not be cured), is it Ok to say that, while viruses/bacteria are becoming stronger, we are getting weaker?
 
No guarantees, man.

Some species of virus or bacteria have been defeated by being eradicated.

In general, microbes adapt when they reproduce. By removing them from most of the population, there are orders of magnitude fewer replications, and therefore much less chance they will adapt in any way. We have not only improved our quality of living, but we have significantly slowed down the rate of adaptation for infectious agents by making them so scarce.

We are not becoming weaker because we are not exposed to these infectious agents - we inherited our ancestors' resistance. If somebody were to drop smallpox back on the planet, our genome still has about the same capacity to defend itself.

Considering our improved overall health, if smallpox were to drop out of the sky today, we'd probably handle it with a lower morbidity and mortality rate than our ancestors did five centuries ago.
 
blutoski said:
No guarantees, man.

Some species of virus or bacteria have been defeated by being eradicated.

In general, microbes adapt when they reproduce. By removing them from most of the population, there are orders of magnitude fewer replications, and therefore much less chance they will adapt in any way. We have not only improved our quality of living, but we have significantly slowed down the rate of adaptation for infectious agents by making them so scarce.

We are not becoming weaker because we are not exposed to these infectious agents - we inherited our ancestors' resistance. If somebody were to drop smallpox back on the planet, our genome still has about the same capacity to defend itself.

Considering our improved overall health, if smallpox were to drop out of the sky today, we'd probably handle it with a lower morbidity and mortality rate than our ancestors did five centuries ago.
Click to expand...

Yes.
Also, even if in the long run human race may become weaker by not being exposed to illnesses (I am not saying it will, just an hypothesis), evolution usually works in the very long run.
Agreed for the smallpox thing
 
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