Naked Science Forum

Life Sciences => Physiology & Medicine => COVID-19 => Topic started by: JohnH on 19/11/2021 10:46:14

Title: Covid-19, High infection rates why no new variants being reported
Post by: JohnH on 19/11/2021 10:46:14
Just curious, with such high infection rates particularly in the UK, are there no new variants emerging. Our identification ability is second to none, so I am very surprised that no knew strains are being reported. Have we scaled back on this?
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Colin2B on 19/11/2021 12:29:15
Probably the press getting hooked on COP26 and the government sleaze and bored with Covid (after all everyone thinks it’s over!)
Latest variant was picked up in October, but Delta is still the dominant form and some of the others have very low measured infections.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: alancalverd on 19/11/2021 12:38:25
That's Darwin for you. After a while, species either separate and occupy different sub-environments, or one variant dominates.'Twas ever thus.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: wolfekeeper on 19/11/2021 21:59:33
The new antivirals will probably be helping. A lot of the previous variants were thought to crop up when people had covid for long periods without dying. It gave the virus a chance to mutate. Now they can just dose them up in hospital with antibodies and antivirals, and they will clear the virus much more quickly.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Petrochemicals on 19/11/2021 22:46:49
Where oh where is a medically trained expert moderator when you want one?

As a pure guess, corona has made the easily mutatable changes it can, there may have been other variants, deadly or transmissible but the combination of both is something the corona virus is struggling to achieve. If mutations where so easily achievable by viruses they would have wiped everything off the planet by now.

If you think about eugenics and the practice of selective breeding, it works for a while, but many traits are lost.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: evan_au on 20/11/2021 06:15:39
WHO is monitoring quite a few variants.
But to displace Delta, it has to be more transmissible than Delta and/or be able to bypass existing immunity to Delta.
See: https://www.ecdc.europa.eu/en/covid-19/variants-concern
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: set fair on 21/11/2021 13:58:05
I think Delta multiples, sheds and infects a new host before the immune memory kicks in, hence anyone can be infected and infect someone else regerdless of vaccination status or previous infection, if the circulating antibody level and covid specific T-cell level is too low to quickly stop an infection with Delta . Delta can do this almost as easily whether the antibodies are specific to Delta or not, it's incubation period is so short that it doesn't need resistance to circulating antibodies, it just needs there not to be enough.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: evan_au on 21/11/2021 18:41:22
Quote from: Zer0
Delta ... infects a new host before the immune memory kicks in
COVID has a gene which suppresses the immune system for about 5 days after infection. Meanwhile the virus replicates and sheds for about 2 days without the victim being aware of it (if they become aware of it at all).
- It's a stealth virus...

The original paper reporting on the ability of Ivermectin to suppress COVID in vitro suggested that:
-  Ivermectin suppresses the ability of proteins to enter the cell nucleus.
- This prevents the virus interfering with the normal immune response to viral infection.
- It's a pity that the dose required too high to be used in a living animal
- Presumably the nucleus needs to be continually aware of what is going on in the cell, so it can control normal cellular functions efficiently. Ivermectin probably interferes with these normal cellular regulation functions, too.

See: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7129059/    and caption on Figure 1G.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Colin2B on 22/11/2021 07:27:46
To add to what @evan_au says, the mutation allows the virus to produce a higher load of viral particles in the body so it is more than 2 times as contagious as other variants. A study from China showed that the viral load was 1,000 times more than that of previous coronavirus strains.
Delta’s incubation is around 4 days, compared to the 5.6 days in other strains, but there is a wide variation between individuals.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: set fair on 22/11/2021 17:14:20

COVID has a gene which suppresses the immune system


Dear God where do you get thie rubbish from?
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: evan_au on 22/11/2021 20:27:44
Quote from: evan_au
COVID has a gene which suppresses the immune system
Interferon is part of the innate immune response, which warns the body of a viral attack, and further triggers protective actions by the immune system.
- It is interferon which gives the classic "cold/flu" symptoms of fever, runny nose, and feeling "blah".
- SARS-COV-2 suppresses the interferon response, which means that people don't know that they are infected, and go about their normal lives.
- The original SARS virus was controlled more easily, because people ran a high temperature when they were infected, and they felt bad, so they stayed away from others. Infra-red cameras at airports picked up incoming infected passengers.
- SARS-COV2 (and MERS, another Coronavirus) block interferon production, so they are harder to control.
- Fortunately, MERS was not nearly as transmissible as SARS-COV2 Delta variant, so it did not turn into a pandemic

So the percentage of people who think "I don't need a COVID vaccine, because I have a strong immune response that will protect me" don't realize that this virus subverts your immune system so it can infect you freely (and your friends and family and colleagues....).

See, for example: https://www.nature.com/articles/s41556-021-00712-y
Quote from: nature
the SARS-CoV-2 nucleocapsid protein represses the antiviral type I interferon response

See, for example, https://www.frontiersin.org/articles/10.3389/fimmu.2020.580641/full
Quote from: Frontiers
CoVs including SARS-CoV and MERS-CoV encode multiple proteins which antagonize (interferon) signaling
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: set fair on 22/11/2021 23:25:36
No mention of a "gene which surpresses the immune system" in either article. It's poteins which which do that.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Petrochemicals on 22/11/2021 23:28:51


So the percentage of people who think "I don't need a COVID vaccine, because I have a strong immune response that will protect me" don't realize that this virus subverts your immune system so it can infect you freely (and your friends and family and colleagues....).
Friends colleagues and family who likewise have spurned the vaccination.

No mention of a "gene which surpresses the immune system" in either article. It's poteins which which do that.
Where are the proetins produced, by what?
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: set fair on 23/11/2021 00:32:20

No mention of a "gene which surpresses the immune system" in either article. It's poteins which which do that.
Where are the proetins produced, by what?


In the ribodomes by the ribosomes.

There are several proteins in CoV2 which dirupt with the interferon response.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Petrochemicals on 23/11/2021 01:29:42

No mention of a "gene which surpresses the immune system" in either article. It's poteins which which do that.
Where are the proetins produced, by what?


In the ribodomes by the ribosomes.

There are several proteins in CoV2 which dirupt with the interferon response.
How are the ribodomes and the  ribosomes created?
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: set fair on 23/11/2021 02:51:51

No mention of a "gene which surpresses the immune system" in either article. It's poteins which which do that.
Where are the proetins produced, by what?


In the ribodomes by the ribosomes.

There are several proteins in CoV2 which dirupt with the interferon response.
How are the ribodomes and the  ribosomes created?

How do ypu think the ribosokes ae created?
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: evan_au on 23/11/2021 09:16:57
Quote from: Set Fair
No mention of a "gene which surpresses the immune system" in either article. It's poteins which which do that.
SARS-COV2 is an infectious pathogen.
- If the proteins that suppressed the interferon/immune response were just stored as proteins, they would be used up when the first cell got infected.
- In fact, these immune-suppressing proteins are coded by genes in the viral RNA
- So that as soon as the human cell gets infected, these viral proteins are churned out by the ribosomes, get into the human cell nucleus, and suppress interferon production.

The viral RNA also gets copied, packaged into new virions, which are released to infect new cells, before the human immune system catches up with the fact that it has a raging infection
- Unfortunately for some people, their immune system then goes into overdrive, attacking everything in sight (a "cytokine storm").

PS: There are some proteins that are "self-replicating", such as the prions which cause mad-cow disease, and perhaps some of the protein masses seen in some neurodegenerative diseases. But it is the viral RNA which codes for the replication of proteins in COVID-19.
See: https://en.wikipedia.org/wiki/Prion
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: set fair on 23/11/2021 10:29:54
Quote from: Set Fair
No mention of a "gene which surpresses the immune system" in either article. It's poteins which which do that.
SARS-COV2 is an infectious pathogen.
- If the proteins that suppressed the interferon/immune response were just stored as proteins, they would be used up when the first cell got infected.
- In fact, these immune-suppressing proteins are coded by genes in the viral RNA
- So that as soon as the human cell gets infected, these viral proteins are churned out by the ribosomes, get into the human cell nucleus, and suppress interferon production.


You're just digging yourself deeper, you try preset yourself as some kind of expert when you're not.
Quote
COVID has a gene which suppresses the immune system
is like saying covid had a gene which allows it to replicate.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Petrochemicals on 23/11/2021 20:00:51

No mention of a "gene which surpresses the immune system" in either article. It's poteins which which do that.
Where are the proetins produced, by what?


In the ribodomes by the ribosomes.

There are several proteins in CoV2 which dirupt with the interferon response.
How are the ribodomes and the  ribosomes created?

How do ypu think the ribosokes ae created?
I do not know what they are, but I think that the corona virus influences them somehow? Please clarify upon them.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: set fair on 23/11/2021 23:37:38

No mention of a "gene which suppresses the immune system" in either article. It's proteins which which do that.
Where are the proteins produced, by what?


In the ribodomes by the ribosomes.

There are several proteins in CoV2 which disrupt with the interferon response.
How are the ribodomes and the  ribosomes created?

How do ypu think the ribosokes ae created?
I do not know what they are, but I think that the corona virus influences them somehow? Please clarify upon them.

Ribosomes are organelles in our cells which synthesis  proteins, Viruses highjack them to produce their proteins. Some viruses also do a good job of stopping them making our own proteins others try to do it on the quiet.

Interferons are messenger proteins, a subset of cytokynes. All vertebrates have them. We have more than twenty different interferons. As far as we're concerned here with covid, their purpose is to invoke various processes (in the cell, in neighbouring cells and white blood cells) to prevent the virus replicating.

Every virus that can infect us has to combat  interferon. Some of their methods are very ingenious and most viruses have multiple methods. Having a relatively small genome, viruses are very economical. The nucleocapsid membrane protein is a structural protein , holding the cell membrane together but additionally it can be released on its own into the host cell where it will antagonize type 1 interferon. It's common for viral proteins to multitask.

Sars CoV-2 doesn't have "a gene which suppresses the immune system", rather it  some genes which code for proteins which have the sole purpose of suppressing the immune response and has parts of other genes which code for parts of structural proteins which suppress the immune system. This is not just normal for viruses, it's essential.

Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Petrochemicals on 24/11/2021 00:13:24

No mention of a "gene which suppresses the immune system" in either article. It's proteins which which do that.
Where are the proteins produced, by what?


In the ribodomes by the ribosomes.

There are several proteins in CoV2 which disrupt with the interferon response.
How are the ribodomes and the  ribosomes created?

How do ypu think the ribosokes ae created?
I do not know what they are, but I think that the corona virus influences them somehow? Please clarify upon them.

Ribosomes are organelles in our cells which synthesis  proteins, Viruses highjack them to produce their proteins. Some viruses also do a good job of stopping them making our own proteins others try to do it on the quiet.


What control process in the viruses allow them to hijack ribosomes?
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: evan_au on 24/11/2021 08:44:57
Quote from: Petrochemicals
What control process in the viruses allow them to hijack ribosomes?
Viruses produce messenger RNA.
Ribosomes translate messenger RNA into proteins.
- The Ribosome does not check whether the mRNA came from the cell's own DNA, an invading virus, or a mRNA vaccine, but will start transcribing mRNA into proteins.
- So effectively, the virus (and mRNA vaccines) hijack the cell's protein-making machinery for their own use.

See: https://en.wikipedia.org/wiki/Ribosome
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: evan_au on 26/11/2021 07:23:28
Quote from: OP
why no new variants being reported
There are new variants arising continually - every chain of infection has a mutation about every 2 weeks, and there are hundreds of thousands of chains of infection.
- However, most of these variants are less infectious than Delta, and so they don't spread very far.
- There is an active network of researchers looking for new variants that seem more transmissible, or more lethal, or which might evade immunity (whether natural or vaccine-induced)

A new variant has arisen in South Africa which seems to be more transmissible than Delta, and WHO is holding a conference to review what is known about it.
- If they consider it a "Variant of Concern", they will give it a Greek letter, instead of the current B.1.1.529
- It does have a lot of mutations, including about 30 in the spike protein alone, which makes it a risk for evading immunity.
- Some countries have blocked flights from Southern Africa, to reduce the chance of it entering their country

See, for example: https://www.nature.com/articles/d41586-021-03552-w
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Bored chemist on 26/11/2021 09:03:01
Sars CoV-2 doesn't have "a gene which suppresses the immune system", rather it  some genes which code for proteins which have the sole purpose of...
That's like saying there's no gene for brown eyes because the brown pigment isn't made of DNA.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: alancalverd on 26/11/2021 10:31:27
And here it is.....https://www.bbc.co.uk/news/uk-59424269

Be careful what you wish for.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: set fair on 26/11/2021 14:21:41

What control process in the viruses allow them to hijack ribosomes?


You might try this I haven't watched this episode, He has a (bad?) habit of using too many abbreviations but otherwise I find him a good source.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Petrochemicals on 26/11/2021 20:56:06

What control process in the viruses allow them to hijack ribosomes?


You might try this I haven't watched this episode, He has a (bad?) habit of using too many abbreviations but otherwise I find him a good source.
No, I don't think that

What control process in the viruses allow them to hijack ribosomes?


You might try this I haven't watched this episode, He has a (bad?) habit of using too many abbreviations but otherwise I find him a good source.
No I don't think that youtube Google alphabet, as powerful as they are control viruses ability to hijack cell commu ications. Is it perhaps a quality produced by genetic information?
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: evan_au on 27/11/2021 10:22:20
B.1.1.529 is now officially dubbed "Omicron", Greek letter "ο".

They skipped 2 Greek letters; some claim the reasons are:
- Nu "ν" because it could be confused as a "New Variant" instead of "ν Variant" (by English speakers)
- Xi "χ", because it is the name of the Chinese head of state

Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Colin2B on 27/11/2021 10:47:46
- Nu "ν" because it could be confused as a "New Variant" instead of "ν Variant" (by English speakers)
Gutting. It would have been fun to have a nu new variant.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: vhfpmr on 27/11/2021 14:51:15
B.1.1.529 is now officially dubbed "Omicron", Greek letter "ο".
It's arrived in the UK. Two cases found, in Chelmsford (12 miles away) and Nottingham. I wonder if we've got a test & trace system that's actually capable of finding the contacts this time around?
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Petrochemicals on 27/11/2021 20:30:49
- Nu "ν" because it could be confused as a "New Variant" instead of "ν Variant" (by English speakers)
Gutting. It would have been fun to have a nu new variant.
Yes, or the new xi variant, it must have fallen victim to the feminists. I think they could have called this variant 'omicron 5', that would have softened the blow
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: evan_au on 28/11/2021 10:20:48
Quote from: Petrochemicals
omicron 5
I assume that is a geeky reference to Star Wars?

A week ago, that would have been an easy find on Google. This week, any mention of 'omicron' brings up stories about COVID variants...
See: https://starwars.fandom.com/wiki/Omicron_5
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Bored chemist on 28/11/2021 10:46:41
it must have fallen victim to the feminists.
What?
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: alancalverd on 28/11/2021 19:00:43
Could happen to anyone. It used to turn up in B movies - last man on the planet, captured by bikini-clad savages to repopulate.... Or was that last night's meaningful dream? 
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Petrochemicals on 29/11/2021 07:24:25
Quote from: Petrochemicals
omicron 5
I assume that is a geeky reference to Star Wars?

A week ago, that would have been an easy find on Google. This week, any mention of 'omicron' brings up stories about COVID variants...
See: https://starwars.fandom.com/wiki/Omicron_5
Pure chance, but that was the point, it is the 5th variant and it sounds exotic, you could type pretty much anything concerning Greeks or Romans into Google and come up with a sifi link.

https://m.imdb.com/title/tt4230950/
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Colin2B on 29/11/2021 13:49:26
B.1.1.529 is now officially dubbed "Omicron", Greek letter "ο".
It's arrived in the UK. Two cases found, in Chelmsford (12 miles away) and Nottingham. I wonder if we've got a test & trace system that's actually capable of finding the contacts this time around?
3rd case in England, 6 in Scotland.
Some of the Scottish cases have no travel connection so it must have already be in the community.

Initial reports from SA suggest symptoms are mild with only unvaccinated going into hospital.
Very idle speculation - if this turns out to be very mild symptoms is it possible that this could be the first move towards CV19 becoming a low impact cold/flu type illness. This could be interesting if it then became the dominant strain. Will be interesting to see the impact on vulnerable groups and consequent effect on hospitals.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: evan_au on 29/11/2021 21:11:16
One of the doctors treating Omicron patients in Africa said that symptoms were different from Delta, and  "infected do not suffer the loss of taste or smell"
In Delta, about 40% of infected people lose their sense of smell (which impacts taste).
If proven, that would be promising. Nerve-supporting cells (astrocytes and microglia) are susceptible to COVID infection as they express the ACE2 receptor; death of these cells is suspected of causing the loss of smell nerves.

These astrocytes and microglia cells also exist in the brain, and death of neurons in the brain is thought to cause the "brain fog" reported by many victims of long-COVID.

Neurons in the nose regenerate after damage; most neurons in the brain do not regenerate. A study of people recovered from COVID infection showed a faster-than-normal loss of brain tissue.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Colin2B on 29/11/2021 23:06:44
One of the doctors treating Omicron patients in Africa said that symptoms were different from Delta, and  "infected do not suffer the loss of taste or smell"
Early reports of a ‘typical patient’ aged 33 who said that he’d been extremely tired for a few days with body aches and pains with a bit of a headache, The patient didn’t have a sore throat, but more of a “scratchy throat” but no cough or loss of taste or smell.

Certainly very different from Alpha and Delta, will be interesting to see the effect on vulnerable patients.
It would certainly be good news if this variant results in less brain fog and less long Covid.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: evan_au on 30/11/2021 08:39:46
Quote from: Colin2B
will be interesting to see the effect on vulnerable patients
I heard that African countries don't tend to have as many elderly people as "Western" countries (as a % of population).
That may make it hard to extrapolate to those elderly people who have been the majority of COVID victims to date in Western countries.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Colin2B on 30/11/2021 08:50:11
Quote from: Colin2B
will be interesting to see the effect on vulnerable patients
I heard that African countries don't tend to have as many elderly people as "Western" countries (as a % of population).
That seems to be true for most poorer countries and even poorer areas in so called richer nations eg Glasgow tenements.
I was thinking that it might be a while before can we see any meaningful effect over here.
I think you said earlier that SA Is mainly unvaccinated, so again big difference.
Wait & see!  :(
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Petrochemicals on 30/11/2021 08:58:52
Quote from: Colin2B
will be interesting to see the effect on vulnerable patients
I heard that African countries don't tend to have as many elderly people as "Western" countries (as a % of population).
That may make it hard to extrapolate to those elderly people who have been the majority of COVID victims to date in Western countries.
Ethnicities who are from these climates though suffer more than those with European heritage.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Colin2B on 30/11/2021 11:24:57
Ethnicities who are from these climates though suffer more than those with European heritage.
Although that is true it doesn't follow that they will have the same response in the country of ethnic origin.
There is sometimes an interesting evolutionary response to a local environment that can be detrimental to health when moving to a different environment, including dietary changes.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: alancalverd on 30/11/2021 14:22:51
Quote from: Colin2B
will be interesting to see the effect on vulnerable patients
I heard that African countries don't tend to have as many elderly people as "Western" countries (as a % of population).
That may make it hard to extrapolate to those elderly people who have been the majority of COVID victims to date in Western countries.
Ethnicities who are from these climates though suffer more than those with European heritage.
Not sure how this plays in other countries, but members of ethnic minorities in the UK generally tend to live at higher densities and spend more time socialising  than the majority. Added to which the ethnic balance of National Health Service and Social Services employees (who have the greatest occupational exposure to infectious diseases) is skewed towards those minorities.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Petrochemicals on 30/11/2021 16:45:47
Quote from: Colin2B
will be interesting to see the effect on vulnerable patients
I heard that African countries don't tend to have as many elderly people as "Western" countries (as a % of population).
That may make it hard to extrapolate to those elderly people who have been the majority of COVID victims to date in Western countries.
Ethnicities who are from these climates though suffer more than those with European heritage.
Not sure how this plays in other countries, but members of ethnic minorities in the UK generally tend to live at higher densities and spend more time socialising  than the majority. Added to which the ethnic balance of National Health Service and Social Services employees (who have the greatest occupational exposure to infectious diseases) is skewed towards those minorities.
Quite right, I think the humidity of the country plays a part also, corona seems to have hit native Americans in the Amazon quite hard indeed.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: alancalverd on 01/12/2021 11:07:17
It's a bizarre coincidence, but the prevalence in Northern Ireland and Wales exceeds that of East Anglia, and Manchester more than London, so maybe humidity is important!
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Petrochemicals on 02/12/2021 22:11:55
It's a bizarre coincidence, but the prevalence in Northern Ireland and Wales exceeds that of East Anglia, and Manchester more than London, so maybe humidity is important!
Wetter countries with cold climates have a higher resistance, but have always had a higher mortality to winter respiratory diseases, the uk being one of the worst. Just above freezing damp is the most awful weather, give me minus 50c any day.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: set fair on 05/12/2021 17:58:41
There are still parts of Europe and the US in the Delta surge and areas of Europe which haven't (yet) had much Delta. The danger is that Delta and Omicron will circulate in the same area and hybridise by recombination and come up with something nasty, on the other hand they might do so and produce something more benign.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: set fair on 11/12/2021 15:47:15
BBC maths from the 9th of december
Quote
About 2,500 daily cases would exceed 100,000 a day by the end of the month, if cases did double every three days.

2,500 x 2^7.33 is actually a tad over 400,000. Though we all know that the exponential growth slows to linear growth. I don't know why they can't get somebody at the BBC who can do simple arithmatic nor why this pretence that growth will be exponetial.
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: Bored chemist on 11/12/2021 17:33:35
BBC maths from the 9th of december
Quote
About 2,500 daily cases would exceed 100,000 a day by the end of the month, if cases did double every three days.

2,500 x 2^7.33 is actually a tad over 400,000. Though we all know that the exponential growth slows to linear growth. I don't know why they can't get somebody at the BBC who can do simple arithmatic nor why this pretence that growth will be exponetial.
Do you realise that 400,000 exceeds 100,000?
And maybe the disparity is precisely because they know that the rate falls with time.
Also, if you plan to complain about them, learn to  spell  "arithmetic" and "exponential".
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: evan_au on 11/12/2021 20:59:53
Quote from: set fair
this pretence that growth will be exponetial.
When there is a "naive" population (never previously been exposed to a pathogen, so they have no resistance):
- And the pathogen has R0 > 1 (eg Delta with R0  around 7; Omicron not clearly known yet)
- And the outbreak has just started, so there is a small number of infected people, and a huge number of susceptible people
- So you can approximate the susceptible population as "infinite" compared to the infected population
- Then the growth will be exponential: Starts off very small, and rapidly grows to be huge
- Exponential growth catches everyone by surprise!

Quote
we all know that the exponential growth slows to linear growth
The main idea of "flattening the curve" is to bend the number of new infections away from exponential growth (Reff < R0) and towards linear growth, and then to no growth (Reff = 1) and then into reduction (negative exponential, Reff < 1).
- Flattening the curve can be achieved by strenuous efforts with mask-wearing, social distancing, contact tracing, isolation, and lockdowns
- Or it can be done with vaccination (if the vaccination rate is high enough, outbreaks will die down)
- Or by just infecting everyone (with associated death toll, overload of hospital system, etc)

This occurs because these methods reduce the number of susceptible people each infected person can infect.
- You can no longer treat the susceptible population as "infinite" compared to the number of infectious people.

If you just let the virus run free, you will end up with something like the "Logistic curve", with an initial exponential growth, a short linear phase in the middle, and a negative exponential tail.
See: https://en.wikipedia.org/wiki/Logistic_function
Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: set fair on 12/12/2021 12:57:10

The main idea of "flattening the curve" is to bend the number of new infections away from exponential growth (Reff < R0) and towards linear growth, and then to no growth (Reff = 1) and then into reduction (negative exponential, Reff < 1).
- Flattening the curve can be achieved by strenuous efforts with mask-wearing, social distancing, contact tracing, isolation, and lockdowns


This is simply not correct. What it will do is lower Reff this will slow the doubling rate but it will still be exponential, not linear.

Probably a signifiant part of the reason that the exponential growth subsides into linear growth has to do with how many contacts different people have. Those with a lot of cantacts will
a) more readily catch Omicron
and
b) when they do, they will infect a lot of people.
so
a) they will make up a disproportionately higher percentage of early Omicron cases
b) Reff will be high at the beginning of the Omicron wave

As time goes on the proportion (in the population) of high contacts / highly susceptible people who haven't been infected will decrease. So the average number of cantacts of the average new case drops with time as the Omicron wave progresses. For this reason Reff steadily drops even with no mitigation.


Title: Re: Covid-19, High infection rates why no new variants being reported
Post by: evan_au on 12/12/2021 22:29:13
Quote from: Set Fair
What it will do is lower Reff this will slow the doubling rate but it will still be exponential, not linear.
The Logistic function shows the total number of people infected.
- The early part is exponential growth Reff > 1; ie like ext where t is time, and x > 0
- The latter part is exponential convergence Reff < 1; ie like 1 - ext where x < 0
- A small part near the middle is linear, but this is still exponential Reff = 1; ie like ext where x = 0
       - The number of cases is constant per week
       - If you add up a lot of constant weeks, you end up with a linear behavior
       - This is because the integral of ext = text = t, when x=0.