Naked Science Forum
Life Sciences => Physiology & Medicine => COVID-19 => Topic started by: set fair on 30/04/2021 16:24:30
-
I'm thinking of a strategy like this:- infect, multiply and as soon as a specific part of the immune system is detected by the virus it multiplies less and sheds more - to get into a new host and produce a lesser immune response in order to make reinfection of the same host, at a later date, easier.
What made me ask this?
The virus has often been said to be good (by viral standards) at evading the immune system - it seems to use more tricks than most. Generally, most symptoms of viral infection are actually caused by the immune system rather than the virus itself, but the viral load of CoV2 is high before any symptoms are noticed. The viral load peaks at about day 6: perhaps the T-cells quickly deal with CoV2 once detected but it would be unusual, even exceptional to start getting the better of a virus in just two days - it would be two days if symptom onset was indicative of infection recognition, especially one that is adept at evading the immune system.
If a strategy can work, then there will be organisms using that strategy.
Bonus points available for spotting the pun in the question.
-
Are any viruses known to make a quick exit once they're rumbled?
That is the strategy used by most viruses - infect quickly, and infect others quickly.
There are some exceptions - after a mild acute infection, HIV has a long incubation time hiding out in the immune system before it makes itself known through slow degradation of the immune system.
See: https://en.wikipedia.org/wiki/HIV
Chicken pox uses both strategies - there is an acute infection which is highly infectious; then it hides out in nerves for many years, to reappear later as shingles.
See: https://en.wikipedia.org/wiki/Chickenpox
-
The "Common Cold", and to a large extent the "Flu" are like that.
Hit hard. Likely in part subvert the immune system to help spread (coughing, sneezing, mucous, etc), then are generally gone in a week or so.
To a large extent, COVID is that way too. Hit hard, then gone. Even those with "long COVID" may have cleared the virus, and are simply dealing with after effects and the immune system.
There are a mix of short "acute" virus infections and chronic infections.
Hepatitis A is almost all acute, while Hep B and Hep C tend to be chronic.
Polio tends to be an acute infection, but can have long-term consequences.
HPV can be either acute or chronic. HIV as mentioned is almost entirely chronic.
-
Thankyou, but you are telling me what everybody already knows. My question was whether any short-visit viruses were known to make a tactical withdrawl ie avoid challenging the immune system. The prevailing assumption is that the many short-lived infections are short lived because the immune system has overcome them. I'm looking for any viruses which change their behavior from infecting more host cells to going all out to find new hosts.
-
change their behavior from infecting more host cells to going all out to find new hosts.
What's the difference?
-
change their behavior from infecting more host cells to going all out to find new hosts.
What's the difference?
Once a virion has left the cell in which it was created it can either infect a new cell in the same host or shed to find a new host.
-
Once a virion has left the cell in which it was created it can either infect a new cell in the same host or shed to find a new host.
Virions can't fly.
They can not tell if the next cell they come across is from the same host, or from someone they got sneezed onto (or whatever).
They are not in any position to make decisions about their fate.
-
Once a virion has left the cell in which it was created it can either infect a new cell in the same host or shed to find a new host.
Virions can't fly.
They can not tell if the next cell they come across is from the same host, or from someone they got sneezed onto (or whatever).
They are not in any position to make decisions about their fate.
To be shed they must exit the body and hitch a ride om a droplet or aerosol. What you call a "decision" could be a response to a chemical cue. Your constant criticism on the forum does a lot more good than harm but sometimes you seem to be just obtuse. If you think "Viruses don't and can't have adaptive behavior" just say so.
-
To be shed they must exit the body and hitch a ride om a droplet or aerosol.
And how do they arrange to do this (or to not do it)?
-
In general we have a range. The less lethal viruses spread very easily from person to person, and are a hit hard and gone.
More lethal viruses tend to be harder to spread.
I'm not sure it has to be that way, but humans, and perhaps even other animals will ignore things that only make them mildly ill, but strongly avoid stuff that make them seriously ill.
To some extent, that even becomes innate. For example, as humans we find mouse and rat feces absolutely repulsive. In fact, we've learned to adopt cats to help with rodent infestations.
On a farm with cows and horses... the cows will eat around the horse apples, and horses will eat around cow patties, but not visa-versa.
Likely such practices among animals are part of hard learned lessons from history.
-
Once a virion has left the cell in which it was created it can either infect a new cell in the same host or shed to find a new host.
Virions can't fly.
They can not tell if the next cell they come across is from the same host, or from someone they got sneezed onto (or whatever).
They are not in any position to make decisions about their fate.
Set fair, the above is the most important point to absorb. Sit with a cup of coffee, tea or any other beverage you prefer and think it through. Qualified people have given up their time to give you the correct answers. You would not get this opportunity at most forums. Have a nice day.
-
(Virions) are not in any position to make decisions about their fate.
In living things, a change in behavior can be evolved, or it can be learned (through epigenetics or synaptic weights).
- Viruses are essentially a package of RNA (or DNA for some other viruses).
- Evolution occurs over many generations, and comes from mutations combined with selective pressure. For a virus like SARS-COV2, a viable mutation appears about every 2 weeks in every chain of transmission (other viruses pick up mutations much more quickly). The main selective pressure is from the immune system (with the immune system perhaps primed by a vaccine).
- Viruses have no neurones or synapses, so they can't learn within the lifespan of an individual, as animals do.
- Most of the viruses that infect humans have a minimal set of genes; disabling one or more of them via epigenetic markers would probably render the virus non-viable*.
So the main form of viral "learning" is from evolution, and this can change the behavior of the virus, over many generations.
-The immune system weeds out less "fit" viruses
- But viruses don't "consciously" make "decisions" to change their behavior
*There are some giant viruses with multiple copies of genes. Disabling some of these would not totally disable the virus. See: https://en.wikipedia.org/wiki/Giant_virus
-
It's not that I'm stupid.
It's not that I don't recognise that evolution can provide a virus with a variety of different properties.
It's that a virus can't tell if the cell it is about to infect is the same host as the one in which it was created. (and as a consequence it cant (anthropomorphically speaking) "decide" to infect it or not.)
It's that a virus can't alter the probability of its being sneezed out, because that's a function of the host's immune system (which is doing the sneezy thing anyway).
A virus can barely tell if the hosts immune system has noticed it yet (in mammals and birds, it can sense the change in temperature due to a fever, but that's about it.
Since it can't detect the change, it can't "act" on it.
I'm not talking about the lack of a brain as the reason why a virus can't make a decision. (because, in a way, evolution can take that role).
I'm talking about the impossibility of it sensing the traits you seem to want it to react to.
-
Infectious organisms aren't just completely go with the flow.
Malaria is a disease of the Plasmodium Protozoa. There are some indications that blood levels of the organism increases during hours with peak mosquito activity, an adaptation to enhance spread.
Viruses don't have intelligence, but have evolved to spread, and are often very selective in the kinds of cells they infect, whether it is upper respiratory tract cells, hoping to be coughed up. Other viruses are selective for the GI tract for fecal/oral transmission. And, others are STDs. And others make growths on skin or mucosa, and transmit with skin contact, or sloughing skin.
And, of course, some viruses like Rabies can cause behavioral changes in their hosts to improve transmission.
-
A virus is not a protozoon.
Viruses "do " things that increase transmission. (Strictly, the exploit wat the host does, to enhance their transmission) So, yes, they cause sneezing and coughing.
But the point remains that, as far as I'm aware, they don't alter their behaviour in response to their surroundings.
And that's what the OP's suggestion would need.
It would be a virus that sometimes does A but sometimes does B.
Are there examples of that?
-
Could Covid-19 cause behaviour changes in humans. Such as pulling off face-masks, going up to each other, embracing and breathing over each other?
Isn't there an example in mice. When they encounter cat urine, they smell it, and get infected by a virus.
Which makes mice lose their innate fear of cats. So instead of running away from a cat, the infected mice go up to it. And get eaten by the cat.
-
As far a
And that's what the OP's suggestion would need.
It would be a virus that sometimes does A but sometimes does B.
Are there examples of that?
Certainly viruses will affect different hosts differently.
So one person may routinely get sinus congestion from a cold, while the next person routinely gets chest congestion.
Herpes will periodically go through phases generally marked by having visible lesions in which the virus is highly infectious, and other phases when there are no visible lesions, and it is minimally infectious.
Chickenpox also goes through a childhood phase when it is highly infectious with lesions over much of the body. Then it goes into a dormant phase when it is not infectious, and largely ignored by the host. Then it may come back as Shingles when it is once again symptomatic, and moderately infectious.
-
Could Covid-19 cause behaviour changes in humans. Such as pulling off face-masks, going up to each other, embracing and breathing over each other?
We already saw that in former President Trump. As soon as he got out of the hospital, he triumphantly ripped off his face mask, and started holding political rallies, proclaiming that he would go through the crowds kissing anybody.
Other viruses like Rabies certainly cause behavioral changes to increase the spread.from host to host.
-
Could Covid-19 cause behaviour changes in humans. Such as pulling off face-masks, going up to each other, embracing and breathing over each other?
We already saw that in former President Trump. As soon as he got out of the hospital, he triumphantly ripped off his face mask, and started holding political rallies, proclaiming that he would go through the crowds kissing anybody.
Other viruses like Rabies certainly cause behavioral changes to increase the spread.from host to host.
When you mention Rabies, that virus is too powerful, as it kills its hosts more than is good for wide-scale spreading.
Hence it is not very prominent in terms of global viral success.
From a viral viewpoint, isn't Covid-19 much more efficient, as it infects more hosts without actually killing them.
-
When you mention Rabies, that virus is too powerful, as it kills its hosts more than is good for wide-scale spreading.
It’s less that it kills and more that it is not easy to transmit.
People usually get rabies from the bite of a rabid animal. It is also possible, but rare, for people to get rabies from non-bite exposures, which can include scratches, abrasions, or open wounds that are exposed to saliva or other potentially infectious material from a rabid animal.
-
Isn't there an example in mice. When they encounter cat urine, they smell it, and get infected by a virus.
You are thinking of Toxoplasmosis, which is a protozoa, which is larger and more complex than a virus.
- Yes, it does cause a change in behavior in mice, making them (lethally) bold
- It also infects humans, through emptying cat litter. There have been studies that suggest that Toxoplasmosis also affects human behavior. I recall one report that was done in the military and found a positive correlation between presence of Toxoplasmosis antibodies and the number of vehicle accidents. (Presumably this correlation would extend to the battlefield?)
Toxoplasmosis does modify operation of the immune system to enable it to spread faster.
- And SARS-COV2 modifies the immune system too, suppressing interferon production.
See: https://en.wikipedia.org/wiki/Toxoplasmosis#Parasitology
Rabies (mentioned above) infects the nerves and does drive animals crazy - to the extent that they are more likely to lose their natural fear of humans, and to bite them, thus spreading the pathogen.
See: https://en.wikipedia.org/wiki/Rabies_in_animals
(Overlap with Colin2B...)
-
Could Covid-19 cause behaviour changes in humans. Such as pulling off face-masks, going up to each other, embracing and breathing over each other?
We already saw that in former President Trump. As soon as he got out of the hospital, he triumphantly ripped off his face mask, and started holding political rallies, proclaiming that he would go through the crowds kissing anybody.
Other viruses like Rabies certainly cause behavioral changes to increase the spread.from host to host.
When you mention Rabies, that virus is too powerful, as it kills its hosts more than is good for wide-scale spreading.
Hence it is not very prominent in terms of global viral success.
From a viral viewpoint, isn't Covid-19 much more efficient, as it infects more hosts without actually killing them.
But the Rabies virus thinks soffitication is a the measure of success and has little time for chavs like the corona viruses
-
To be shed they must exit the body and hitch a ride om a droplet or aerosol.
And how do they arrange to do this (or to not do it)?
Sorry to be so long replying - suffereing the slings and arrows of outragious immoderators.
How they might arrange to do this, is what I am hoping to figure out. The reason for the question was to find out if there were any viruses which are known to do this and investigate from there.
-
To be shed they must exit the body and hitch a ride om a droplet or aerosol.
And how do they arrange to do this (or to not do it)?
Sorry to be so long replying - suffereing the slings and arrows of outragious immoderators.
How they might arrange to do this, is what I am hoping to figure out. The reason for the question was to find out if there were any viruses which are known to do this and investigate from there.
Do you understand the idea of a rhetorical question?
-
I'm looking for any viruses which change their behavior...
Other viruses like Rabies certainly cause behavioral changes to increase the spread from host to host.
Lets clarify this - the virus does not change viral behavior from one mode to another.
The virus changes the behavior of the host organism.
-
I'm looking for any viruses which change their behavior...
Other viruses like Rabies certainly cause behavioral changes to increase the spread from host to host.
Lets clarify this - the virus does not change viral behavior from one mode to another.
The virus changes the behavior of the host organism.
Sorry, loose wording there might have given the wrong impression.
Yes, it is the host behaviour that changes. In this case a tendency to paranoia/aggression caused by the effect on the brain.
-
To be shed they must exit the body and hitch a ride om a droplet or aerosol.
There are a number of ways a virus might exit/enter the body.
We are familiar with respiratory viruses.
However there are many other types of viral spread.
- At least one virus is known as the "Kissing Virus"
- Blood borne viruses get spread by contact with blood, or various body fluids, perhaps sexual activities
- Fecal Oral viruses are common. Good hygiene helps, but may not 100% prevent transmission.
Bacteria, of course, are different from viruses, but one can also discuss toxins, either produced during the infection, or produced in a food product prior to consumption.
-
My question was in the hope of finding a steer to find more information. Not a suggestion that I think the idea particularly likely. If there were a disjoin between viral load ans shedding, it could easily missed in a respiatoy disease like covid since, as far as can see, viral load for covid is inferred from swabs, ie shedding is used to infer viral load.
-
My question was in the hope of finding a steer to find more information.
And we answered it.
Which part of "no" are you not understanding?
-
All viruses are trying to make a quick exit all of the time, it's the nature of viruses.