Delta Variant as Contagious as Chicken Pox

Updated:   Published

Specializes in Specializes in L/D, newborn, GYN, LTC, Dialysis.
Quote

The Delta variant is much more contagious, more likely to break through protections afforded by the vaccines and may cause more severe disease than all other known versions of the virus, according to an internal presentation circulated within the Centers for Disease Control and Prevention.

Dr. Rochelle P. Walensky, the director of the agency, acknowledged on Tuesday that vaccinated people with so-called breakthrough infections of the Delta variant carry just as much virus in the nose and throat as unvaccinated people, and may spread it just as readily, if less often.

Well, that's eye-opening.

Read in entirety:

C.D.C. Internal Report Calls Delta Variant as Contagious as Chickenpox

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We could all use some good news ? I am actually quite hopeful. We have a long way to go, especially globally, but there is definitely light at the end of the tunnel.

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Specializes in Emergency Department.

Sorry to be a pessimist macawake but there is now this (my bold):-

The WHO and the UK Government are continuing to track the spread of the Lambda variant of coronavirus, which has become the dominant strain in Peru. The new variant, which has also been called C.37, accounts for 71 per cent of all COVID-19 cases in Peru from January to June 2021.

Peru’s Minister of Health, Óscar Raúl Ugarte Ubilluz, said that the Lambda strain has now spread around the world.

“[The Lambda variant] has been identified in the United States, Chile, Brazil, Argentina, Ecuador, Mexico, Spain, Germany, not only in Peru. 623 samples from 19 regions have been studied since April, through what is called genomic sequencing, that is, the genomic analysis in its composition, to determine the currently circulating variants.”

https://www.sciencefocus.com/news/lambda-variant/

 

 

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1 hour ago, GrumpyRN said:

Sorry to be a pessimist macawake but there is now this

 

I took some liberties with the editing. Great video by the way ? And still I like you even when you’re being a pessimist ?


Oh, I keep my eye on the entire Greek alphabet. Unfortunately there are quite a few variants out there. At least for now, lambda, remains a variant of interest and hasn’t been upgraded to the status variant of concern. We don’t know a lot about it yet. We’ll have to wait and see if it takes off. As far as I know there haven’t been many cases of community transmission outside of several South American countries. The cases we’ve seen in Europe so far, have as far as I’m aware been mostly travel related. But of course that could change. It’s worth keeping an eye on, but I don’t think we should panic.

 

https://www.gavi.org/vaccineswork/covid-lambda-variant-now-29-countries-what-evidence-do-we-have-its-more-dangerous
 

https://www.ecdc.europa.eu/en/covid-19/variants-concern

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Specializes in NICU, PICU, Transport, L&D, Hospice.

If it sticks to pattern, Lambda will be more contagious and slightly more virulent.  Delta is now sporting an RO of 8ish? It started at 2-3, right? How many variants and seasons until it's closer to measles in transmissability? If only the belligerent anti mask and antivaxxers had any idea what it is they are doing. 

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Specializes in Specializes in L/D, newborn, GYN, LTC, Dialysis.
11 hours ago, toomuchbaloney said:

If it sticks to pattern, Lambda will be more contagious and slightly more virulent.  Delta is now sporting an RO of 8ish? It started at 2-3, right? How many variants and seasons until it's closer to measles in transmissability? If only the belligerent anti mask and antivaxxers had any idea what it is they are doing. 

IF only. I doubt most even care.

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I’m sure many already know this, but since media often reports Covid’s R0, I’d like to talk a bit about the term. When I say ”a bit”, that’s probably a lie. I suspect that this post might end up long and rambling, like so many of my posts do ?

R0 (R nought) is the basic reproduction number of a pathogen. R0 is the number of new (secondary) cases that one infected individual will generate in a completely susceptible population. 

If R0 of a pathogen is for example estimated to be three, each infected individual will be assumed to infect three others. That doesn’t have to be true on an individual basis. For example, one individual might infect zero others, while another infected person might infect six people. The 3 in R0 = 3 is an average. 

While R0 does have a definitive value in a certain population and location, at a given point in time, the value is estimated by using mathematical models with several assumptions put into the model. 

In the early days of a pandemic with a novel pathogen, when the properties of the pathogen are largely unknown and the capacity for widespread testing is lacking, it is very hard to estimate the R0 accurately. You can only guesstimate using what early data you have and whatever is known about the behavior of other (similar) pathogens in a population. Despite the very start of an outbreak being the most ideal time to calculate R0 (since the entire population can be assumed to be naive and susceptible), R0 is almost always estimated retrospectively.

A lot of factors can go into the mathematical model. How long is an infected person infectious? What does the population contact rate and mixing look like? Do various subgroups of the population mix homogeneously or heterogeneously? Age? Geography? Urban/rural? Time? What’s the likelihood of infection per contact?

The mathematical model will look at both the biological characteristics/properties of the disease-causing agent and human behavior and interaction. The assumptions/variables that are included in the model can of course have a significant impact on the result the model produces.

Remember that I started off by saying that R0 is applicable on a completely susceptible population? 

Vaccinations can remove susceptible members of a given population. That’s kind of the reason we’re vaccinating (and why I and others keep harping on about the importance of getting vaccinated ?). When attempting to measure the effect of vaccination it is much more relevant to look at the Effective Reproduction number, Re. Unlikely R0, Re does not assume that the entire population is susceptible. 

I’m going to include a link that’s from the U.K. and slightly over a month old, and it estimated the then current effective reproduction number (in England) of Alpha as 0.8 and Delta as 1.5. (The UK has one of the highest vaccine coverages in the world and still had some restrictions in place at the time when this was published). 

https://www.imperial.ac.uk/news/223853/delta-variant-could-cause-significant-third/

The reason I posted the above is just to show that the effective reproduction number can be much lower than R0, the basic reproduction number.

(The mathematical model estimates of the Delta variant R0 that I’ve seen are in the 5-8 range).

When I look at R0 numbers reported by the media, I always view them in the context of all the other factors that are currently influencing a population.

While I have no doubt that the Alpha variant is more transmissible than the original SARS-CoV-2 virus, and that Delta is more transmissible than Alpha, I feel that simply reporting R0 doesn’t paint the whole picture. I’m not in the least bit happy that transmissibility has made two significant jumps already, but I’m much more focused on the effective reproduction, than R0, and ultimately on hospitalization and mortality rates.

When I see the R0 increase, my primary concern is for the parts of the world that still have a much larger percentage of their populations susceptible. 

Getting the effective reproduction number consistently below one, is our way out of the pandemic. Making sure that all countries in the world, not just the one we happen to live in, vaccinated a large part of their respective populations, is our way out of this pandemic.

What can we do? A lot actually. And now that we have vaccines, they are the major player. 

If I’m honest I’m a bit annoyed that some media keep reporting R0 without fully explaining what it is. I think the effect is a bit doomsdayish (yes, I know that’s not really a word ?). I prefer that people get vaccinated because they understand the benefits to themselves and to society as a whole, not because the headlines scare them. 

This post turned out to be exactly as rambling as I feared. I really shouldn’t try to write posts when I’m tired and caffeine-wired at the same time ?

Now I’m going to go looking for some sources that explain this more clearly than I have. I’ll add them later on, if I can find them.

Edited to add:

These two look promising. I’ve only speed read them, but they certainly look much less rambling than my explanation ? and demonstrate why epidemiology isn’t always easy.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6302597/

https://www.the-scientist.com/features/why-r0-is-problematic-for-predicting-covid-19-spread-67690

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22 hours ago, toomuchbaloney said:

If it sticks to pattern, Lambda will be more contagious and slightly more virulent.

There’s still much that we don’t know about the Lambda variant, but I don’t think there will necessarily be a linear increase in transmissibility (and hope that there won’t be). I could be wrong, but I don’t think that Delta was ever the dominating variant in Peru? Don’t quote me on this, but I think it is Gamma that Lambda has now ”outmaneuvered” and dominated. 
 

I found this interesting:

https://www.nationalgeographic.com/science/article/the-unusual-lambda-variant-is-rapidly-spreading-in-south-america-heres-what-we-know
 

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Specializes in NICU, PICU, Transport, L&D, Hospice.
1 hour ago, macawake said:

I’m sure many already know this, but since media often reports Covid’s R0, I’d like to talk a bit about the term. When I say ”a bit”, that’s probably a lie. I suspect that this post might end up long and rambling, like so many of my posts do ?

R0 (R nought) is the basic reproduction number of a pathogen. R0 is the number of new (secondary) cases that one infected individual will generate in a completely susceptible population. 

If R0 of a pathogen is for example estimated to be three, each infected individual will be assumed to infect three others. That doesn’t have to be true on an individual basis. For example, one individual might infect zero others, while another infected person might infect six people. The 3 in R0 = 3 is an average. 

While R0 does have a definitive value in a certain population and location, at a given point in time, the value is estimated by using mathematical models with several assumptions put into the model. 

In the early days of a pandemic with a novel pathogen, when the properties of the pathogen are largely unknown and the capacity for widespread testing is lacking, it is very hard to estimate the R0 accurately. You can only guesstimate using what early data you have and whatever is known about the behavior of other (similar) pathogens in a population. Despite the very start of an outbreak being the most ideal time to calculate R0 (since the entire population can be assumed to be naive and susceptible), R0 is almost always estimated retrospectively.

A lot of factors can go into the mathematical model. How long is an infected person infectious? What does the population contact rate and mixing look like? Do various subgroups of the population mix homogeneously or heterogeneously? Age? Geography? Urban/rural? Time? What’s the likelihood of infection per contact?

The mathematical model will look at both the biological characteristics/properties of the disease-causing agent and human behavior and interaction. The assumptions/variables that are included in the model can of course have a significant impact on the result the model produces.

Remember that I started off by saying that R0 is applicable on a completely susceptible population? 

Vaccinations can remove susceptible members of a given population. That’s kind of the reason we’re vaccinating (and why I and others keep harping on about the importance of getting vaccinated ?). When attempting to measure the effect of vaccination it is much more relevant to look at the Effective Reproduction number, Re. Unlikely R0, Re does not assume that the entire population is susceptible. 

I’m going to include a link that’s from the U.K. and slightly over a month old, and it estimated the then current effective reproduction number (in England) of Alpha as 0.8 and Delta as 1.5. (The UK has one of the highest vaccine coverages in the world and still had some restrictions in place at the time when this was published). 
 

https://www.imperial.ac.uk/news/223853/delta-variant-could-cause-significant-third/


The reason I posted the above is just to show that the effective reproduction number can be much lower than R0, the basic reproduction number.

(The mathematical model estimates of the Delta variant R0 that I’ve seen are in the 5-8 range).

 

When I look at R0 numbers reported by the media, I always view them in the context of all the other factors that are currently influencing a population.

While I have no doubt that the Alpha variant is more transmissible than the original SARS-CoV-2 virus, and that Delta is more transmissible than Alpha, I feel that simply reporting R0 doesn’t paint the whole picture. I’m not in the least bit happy that transmissibility has made two significant jumps already, but I’m much more focused on the effective reproduction, than R0, and ultimately on hospitalization and mortality rates.

When I see the R0 increase, my primary concern is for the parts of the world that still have a much larger percentage of their populations susceptible. 

Getting the effective reproduction number consistently below one, is our way out of the pandemic. Making sure that all countries in the world, not just the one we happen to live in, vaccinated a large part of their respective populations, is our way out of this pandemic.

What can we do? A lot actually. And now that we have vaccines, they are the major player. 

If I’m honest I’m a bit annoyed that some media keep reporting R0 without fully explaining what it is. I think the effect is a bit doomsdayish (yes, I know that’s not really a word ?). I prefer that people get vaccinated because they understand the benefits to themselves and to society as a whole, not because the headlines scare them. 
 

This post turned out to be exactly as rambling as I feared. I really shouldn’t try to write posts when I’m tired and caffeine-wired at the same time ?
 

Now I’m going to go looking for some sources that explain this more clearly than I have. I’ll add them later on, if I can find them.



Edited to add:

These two look promising. I’ve only speed read them, but they certainly look much less rambling than my explanation ? and demonstrate why epidemiology isn’t always easy.

 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6302597/
 

https://www.the-scientist.com/features/why-r0-is-problematic-for-predicting-covid-19-spread-67690

I really appreciated the NIH link.  I'll save the other for later thank you!

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17 minutes ago, toomuchbaloney said:

I really appreciated the NIH link.  I'll save the other for later thank you!

You’re most welcome ? 

Even though I chose it because it offered a good general explanation of R0, I must say that I found the parts about the measles R0 quite fascinating. 

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Specializes in CRNA, Finally retired.

I wonder what the RO of the Omega varient will be!

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Specializes in Adult Internal Medicine.
15 hours ago, subee said:

I wonder what the RO of the Omega varient will be!

Stayed tuned, it's coming up after the next break 

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