[Petrochemicals]

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.

[Colin2B]

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.

[alancalverd]

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.

[Petrochemicals]

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.

[alancalverd]

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!

[Petrochemicals]

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.

[set fair]

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.

[set fair]

BBC maths from the 9th of december

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.

[Bored chemist]

BBC maths from the 9th of december

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".

[evan_au]

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!

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 (R_eff < R₀) and towards linear growth, and then to no growth (R_eff = 1) and then into reduction (negative exponential, R_eff < 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

[set fair]

The main idea of "flattening the curve" is to bend the number of new infections away from exponential growth (R_eff < R₀) and towards linear growth, and then to no growth (R_eff = 1) and then into reduction (negative exponential, R_eff < 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 R_eff 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) R_eff 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 R_eff steadily drops even with no mitigation.

[evan_au]

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 R_eff > 1; ie like e^xt where t is time, and x > 0
- The latter part is exponential convergence R_eff < 1; ie like 1 - e^xt where x < 0
- A small part near the middle is linear, but this is still exponential R_eff = 1; ie like e^xt 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 e^xt = te^xt = t, when x=0.