This newest variant of Covid has been dubbed omicron rather than epsilon. If we're following the convention, why have we suddly jumped so far from delta in the Greek alphabet? Anyone know?
CD.
--
"There are, besides, eternal truths, such as Freedom, Justice, etc., that are common to all states of society. But Communism abolishes eternal truths, it abolishes all religion,and all morality, instead of constituting them on a new basis; it therefore acts in contradiction to all historical experience."
It's not hard to find that they didn't skip anything other than those two. Previous variants of the virus have been named by all the prior letters in the Greek alphabet.
Seems they skipped Xi because it is a common last name (like some guy who's the leader of a really powerful country in the far east). I'm wondering why they didn't skip Omicron. I mean, do you really want to piss of this guy?
A bit like with storms they have tagged each variant of concern with a new Greek letter. The intervening ones have all been named but did not propagate very widely having been utterly trounced in the infectivity stakes by Alpha (aka Kent variant) and Delta (aka Indian variant) which each went global and displaced most other strains in the process.
A handy side effect of this is that the characteristic pattern for alpha on the PCR test (2 out of three tags show up) allows a quick scan for the new nasty Omicron strain since it is sufficiently unlike Delta. UK is seeing a few community infections in Scotland with no obvious connection to Africa (we DNA sequence about 20% of all positive PCR tests)
Going forwards they will genetically sequence 100% of those that are masquerading as Alpha (since they could be the new Omicron strain).
formatting link
There is a WHO list of the various strains somewhere. However for some reason their most accessible list is incomplete. The wayback machine will show you when the inbetweener variants were briefly a hot topic. They mostly fell by the wayside when Delta and Delta+ went global.
formatting link
CDC has the least incomplete list now that I have been able to find:
formatting link
They should probably be a bit more Spartan about giving them fancy names until they have to be in the news. As one UK surgeon wryly put it this morning - given how slowly the UK government has responded to the risk of every previous strain you have to wonder if they know more about the nastiness of the new Omicron strain than they are letting on.
Clearly one should be very worried when we get to the Omega strain.
Can you explain the mechanics of how the infectiousness of one strain impacts the spread of another strain? How exactly is a strain of Covid-19 "displaced"?
If a person is infected predominantly by a given strain, they spread the disease based on the number of people they come in contact with and the degree by which they try to minimize the spread of the disease. There is no shortage of potential infectees so there is no competition at that level. To each strain of the virus the world is an all you can eat buffet and no waiting line.
R for the more infective strains Alpha and Delta are greater than one by some margin over the other forms. After a few weeks the ratio of Delta and/or Alpha to the lesser strains is around three orders of magnitude. It is an effect of exponential growth or decay in real life.
Put another way the measures to try and contain the most infective strains of the virus take R for the less infective strains below 1.
Table 3 (p12) in in the UK reports of genotype as a function of time clearly display that Alpha and Delta between them have carved up the territory. Alpha has not decayed away as much as I had thought though (presently it is 80:20 for Delta whereas a month ago it was 25:75)
formatting link
formatting link
In the UK at least you are completely wrong. The measures put in place to try and limit spread of Alpha and Delta have been more than adequate to drive all but Beta into near total oblivion. Kappa was just clinging on by its fingernails both were down at levels <0.1% of all UK cases. The others were one or two more orders of magnitude lower still.
The most recent data no longer shows the same table. They are starting to fret about the novel combinations present in Omicron and analysis is concentrating on that with lots of incomprehensible coloured diagrams.
So the strains do not interact in any way. You are suggesting that the infectible population takes more effective measures to stop the spread of the disease. This is not competition. It would be useful to stop referring to it as such.
You contradict yourself. You say there is competition between strains and then show Alpha and Delta coexisting. Were the strains truly competing one of those two strains would have won out by now. The mechanism you describe is simply the disease competing with the actions of the hosts to prevent infection. Are you saying that if the delta and alpha strains were not present the public would behave in a way to maintain a high level of infection from other strains? In effect, public reaction is a control loop that maintains a high level of infection? Even if so, this is still not competition between strains.
The bottom line is the infection rates are a function of how well each strain survives in the environment. Competition occurs when the different strains interact, i.e. compete for a scarce resource. Infectible hosts for Covid-19 are not scarce. They exist at some level by which any given strain will survive or not. That's not competition between the strains.
Data is scarce. Give it a few weeks. By Christmas we should know more about how many we can expect to be infected by Christmas.
The strains do interact - but only by getting the attention of the population and the public health advice-givers.
It is exactly competition - each strain tries to infect as many people as it can get at. Lock-downs masking-wearing and getting vaccinated make it harder for the strains to infect new victims, but they al work equally well against every strain - the more infective strain still infects more of the people it can get at.
That isn't how it works. Delta is more infectious than Alpha (though not spectacularly so) so more people end up with Delta than Alpha - after a month Delata was ahead by 4:1, when it started of behind by 3:1.
More infections encourage people to take more care not to get infected. Health advice gets delivered more enthusiastically when the intensive care wards start to fill up.
There's nothing active about the competition - everybody infected breathes out virus-loaded droplets. The more infectious strains need their victims to inhale fewer droplets to have an equal chance of getting infected.
There's loads of data around - in Europe and the US thousands get infected every day, and every last one is a data point. Not every positive PCR test gets followed up by sequencing the genome to find out which strain is involved - someone said about 10% were sequenced (at least in first world countries).
Rick C snipped-for-privacy@gmail.com wrote in news: snipped-for-privacy@googlegroups.com:
Testing showing D5 infections rising and other variants falling and even disappearing.
Pretty easy math there. How'd you miss that simple common sense observsation. And the CDC stats will confirm it. The others will die out completely as D5 proliferates.
Now we have O and we have yet to see what it will do.
You are stupid beyond measure if you cannot grasp the simple fact that if two strains A, B have transmission rates of k and k(1+e) with e>1
The ratio of the number of cases B:A grows faster like (1+e)^N
*EXPONENTIALLY*
And yes *I AM SHOUTING*! You are stupid beyond measure if you cannot grasp this basic point.
It doesn't have to be that scarce. The vaccine has seen off some of the older strains almost completely in the UK. Just the odd sporadic sighting. We sequence 20% of all hard positive PCR tests in the UK. (only worth sequencing them if there is plenty of viral DNA)
The UK PCR test being used is also capable of tracking 4 strains of concern at present in its own right. They check 3 loci and they are chosen so that wild, Alpha, Delta and one other can be distinguished.
Most virologists think it will likely be extremely transmissible, able to defeat one of the first line treatments and double dose vaccination. They hope vaccination will make it less severe. It remains to be seen if they are right. Minor levels of community transmission has been seen in Scotland and elsewhere in Europe. So far most cases have been sporadic associated with travel to and from Africa. Hence the travel restrictions and isolation requirements (perhaps already too late). Latest is they have traced it to a single event with all of the cases so far at it.
One big problem with exponential growth is that if you don't eliminate every last case it only takes a very short period of time with an R~3 to go to hell in a handcart. UK levels remain stable on a very high baseline ~40k so we will really struggle to see it growing at first.
No one disputes that point. What you can't seem to grasp is that this simple fact has nothing to do with two strains "competing" with one another. The growth rate of one strain does not impact the growth rate of the other strain. That's what competition is.
"You are stupid beyond measure if you cannot grasp this basic point."
Yes, the VACCINE has seen off older strains. This has nothing to do with competition between strains.
We can try to fight these strains, but with a significant fraction of the population unwilling to do what is required to prevent the spread of the disease until infection numbers rise dramatically, they act as a control loop maintaining minimum infection levels allowing new strains to develop. The fact that the wealthy countries aren't willing to do what is required to immunize the poorer countries is a big factor as well.
On Tuesday, 30 November 2021 at 09:14:32 UTC-8, snipped-for-privacy@gmail.com wrote: ....
Surely it does if there s cross-immunity.
If one strain infects somebody so that they are less likely to get the either strain again for some time there is competition between the two strains. The strain that is more infective will tend to reduce the other to the point of extinction.
No, immunity still has the same impact on both strains. If one strain creates immunity to the other strain and the other strain does not create immunity to the one strain, you might see some impact... but the infection rates are not high enough for this to matter. That's the point. Competition requires some resource to be in short supply limiting infection rates. The success of one strain has to reduce the opportunity for other strains to spread. In this pandemic infection rates are not high enough for any cross effects to matter (so no real competition) and even the vaccine rates are barely high enough to have an impact on strain spreading, still not high enough to have the impact we'd like.
We we have many strains all working against the wall of vaccination to spread among the population independent of one another.
That wouldn't explain the complete eradication of the alpha variant. I understand your argument and am inclined to follow it but I believe there is another effect at work, with delta actively pusing alpha out.
I didn't think the alpha variant was wiped out. But some strains no doubt have been. The reason is simple. The protections we are throwing up combined with the vaccine has pushed the R value for the alpha strain below 1.0. Any organism that has an R value below 1.0 decreases in numbers until it is gone. You should understand that pretty well.
The only reason different strains interact is when one is so much more infectious that it dominates by reproducing much faster pushing up the overall infection numbers significantly. That was what happened with Delta. The world responded to the high rates of infection and strains with lesser infection rates dropped from the scene. So there is some interaction if a strain so completely dominates that it changes behavior in the host affecting the environment to select for more infectious strains causing some to die out entirely. As we all know, it is rare that our precautions last long enough for that sort of thing to happen, at least it seems that way. In much of the US we aren't even wearing masks anymore and infection rates are rising. So I'm pretty sure the Alpha strain is not gone yet and is likely growing in numbers. You can't tell this by looking at percentages. As I've said, each strain is separate, fighting its own battle for survival just as if it were an entirely separate disease. You have to get raw numbers to see it, which is hard to do.
Your idea that Delta is "actively" pushing Alpha out doesn't hold water. They typically aren't even infecting the same people. They just don't interact.
Ed Lee gets some sort of mutation numbers which only he can turn into values for strains, but I don't know I can trust his results as no one else understands what he is saying and he won't show his math.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.