Viral load is roughly 1,000 times higher in people infected with the Delta variant than those infected with the original coronavirus strain, according to a study in China.
John
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Viral load is roughly 1,000 times higher in people infected with the Delta variant than those infected with the original coronavirus strain, according to a study in China.
GrahamPlatt wrote:So is this still entirely down to the changes in the spike protein, enabling more efficient cell penetration, or is there something about it that speeds up its ability to replicate within cells?
redsturgeon wrote:https://www.nature.com/articles/d41586-021-01986-wViral load is roughly 1,000 times higher in people infected with the Delta variant than those infected with the original coronavirus strain, according to a study in China.
John
onthemove wrote:redsturgeon wrote:https://www.nature.com/articles/d41586-021-01986-wViral load is roughly 1,000 times higher in people infected with the Delta variant than those infected with the original coronavirus strain, according to a study in China.
John
More of it in the blood doesn't really seem a satisfactory answer as to how or why the delta variant is "able" to spread so well (title of thread).
redsturgeon wrote:https://www.nature.com/articles/d41586-021-01986-wViral load is roughly 1,000 times higher in people infected with the Delta variant than those infected with the original coronavirus strain, according to a study in China.
redsturgeon wrote:https://www.nature.com/articles/d41586-021-01986-wViral load is roughly 1,000 times higher in people infected with the Delta variant than those infected with the original coronavirus strain, according to a study in China.
John
redsturgeon wrote:
Who mentioned more of it in the blood?
John
"What is Viral Load?
Viral load refers to the amount of virus in an infected person’s blood." https://www.news-medical.net/health/Wha ... -Load.aspx
onthemove wrote:redsturgeon wrote:
Who mentioned more of it in the blood?
John
You did - at least in what you quoted (which was the substance of your post).
Here's what you quoted (my bold)... "Viral load is roughly 1,000 times higher in people infected with the Delta variant than those infected with the original coronavirus strain, ..."
Here's what viral load is..."What is Viral Load?
Viral load refers to the amount of virus in an infected person’s blood." https://www.news-medical.net/health/Wha ... -Load.aspx
redsturgeon wrote:Interesting. The papers only mention the use of PCR testing and not whether blood samples or nose/throat swabs were used. I assumed they would be using swabs.
John
"Virus amplification and sequencing
245 Total RNAs were extracted from oropharyngeal swab samples by using QIAamp Viral
246 RNA Mini Kit (Qiagen, Cat. No. 52904). Virus genomes were generated by two
247 different approaches, (i) using commercial sequencing kit of BGI (ATOPlex
248 1000021625) and sequencing on the BGI MGISEQ-2000 (n=25), and (ii) using
249 version 3 of the ARTIC COVID-19 multiplex PCR primers
250 (https://artic.network/ncov-2019) for genome amplification, followed by library
251 construction with Illumina Nextera XT DNA Library Preparation Kit and sequencing
252 with PE150 (n=63) or SE100 (n=38) on Illumina Miniseq. We report only
253 high-quality genome sequences for which we were able to generate >95% genome
254 coverage. " https://www.medrxiv.org/content/10.1101 ... 2.full.pdf
"Conclusions: NPS [nasopharyngeal swabs] had significantly higher SARS-CoV-2 detection rate, sensitivity, and viral load than OPS [oropharyngeal swabs].(...) NPS should be recommended for (...) and monitoring SARS-CoV-2 load. " https://www.frontiersin.org/articles/10 ... 00334/full
onthemove wrote:redsturgeon wrote:Interesting. The papers only mention the use of PCR testing and not whether blood samples or nose/throat swabs were used. I assumed they would be using swabs.
John
I wasn't sure what to assume, because I wasn't sure if sticking a swab up your nose or back of throat could provide a suitable viral load measurement, (vs just being useful for detecting if the virus is there or not, with the risk of 30% false negatives, etc).
That's why I first googled viral load to try to understand what it specifically refers to and came across that link that I provided that said it was in relation to blood. I've also come across a few other links from seemingly reputable sources that also say viral load is usually measured in relation to blood or plasma.
Which I can understand, because a volume of blood is easily measurable, so it's easy to see how you could get a parts-per-volume measurement.
I'm less clear how you can get a parts-per-volume measurement from a swab... I mean, how do you know how much volume you have in the swab?
But further googling does suggest that nose and throat swabs are used for measuring viral load, albeit, they each tend to give significantly different results. Though it's not clear whether that's because of the nature of how they work, or whether that's because there are genuinely different viral loads in those place - or a mix of the two.
I've gone to the original paper that the Nature article seems to be based upon, and they do mention - buried away in the details - they were using throat swabs..."Virus amplification and sequencing
245 Total RNAs were extracted from oropharyngeal swab samples by using QIAamp Viral
246 RNA Mini Kit (Qiagen, Cat. No. 52904). Virus genomes were generated by two
247 different approaches, (i) using commercial sequencing kit of BGI (ATOPlex
248 1000021625) and sequencing on the BGI MGISEQ-2000 (n=25), and (ii) using
249 version 3 of the ARTIC COVID-19 multiplex PCR primers
250 (https://artic.network/ncov-2019) for genome amplification, followed by library
251 construction with Illumina Nextera XT DNA Library Preparation Kit and sequencing
252 with PE150 (n=63) or SE100 (n=38) on Illumina Miniseq. We report only
253 high-quality genome sequences for which we were able to generate >95% genome
254 coverage. " https://www.medrxiv.org/content/10.1101 ... 2.full.pdf
I must admit, I'm surprised that they can get a 'measurable' - as in being able to quantify - the viral load from a swab in a reliable and comparable way, rather than just looking at a rough and ready threshold to establish a 'positive' test result.
After a bit of googling to try to understand a little more about how viral load can be established from such swabs, I've not yet got a definitive understanding (specifically how they quantify the volume in the sample in the swab so that they can then relate the number of viral particles to that volume), but have come across this article in my search..."Conclusions: NPS [nasopharyngeal swabs] had significantly higher SARS-CoV-2 detection rate, sensitivity, and viral load than OPS [oropharyngeal swabs].(...) NPS should be recommended for (...) and monitoring SARS-CoV-2 load. " https://www.frontiersin.org/articles/10 ... 00334/full
But then, perhaps that research reported in the Nature article was specifically looking at throat swabs on the presumption (?) that this would be the most relevant to transmission(coughing/breathing?)
Or perhaps this new paper is saying that the load with the delta variant is now higher in the throat(?) compared to previous variants.
It does feel a bit poor that they haven't been much clearer about what viral load it is they are referring to and how they measured it.
I mean, there's quite a difference in how I would read...
- 'viral load is 1000x higher with the delta variant'
vs
- 'viral load in the throat is 1000x higher with the delta variant'
After spending much more time now looking into this than I ever intended to, I'm now more inclined to read the nature article as saying the latter, not the former.
Which puts it in quite a different perspective, as (iirc) I've already seen plenty of papers referenced reporting that the different variants can result in different quantities of the virus being present in different areas of the anatomy.
Like I mentioned in an earlier post, I did question how a 1000x viral load wouldn't result in a much more serious outcome for the infected patient.
And this probably provides the answer... if that 1000x viral load is just in the throat, and not the blood, etc, then potentially it's a little more 'out of the way' and less of a problem for the infected patient and could perhaps therefore explain why it doesn't automatically mean you'd expect the patient to be sicker.
If only the paper and article had been clearer about that up front!
redsturgeon wrote:
I guess my assumption was based on the fact that the thousands of coronavirus PCR tests we have personally been involved with have all been throat and/or nasal swabs.
Assumptions are of course not recommended but appear to be correct in the instance.
John
GrahamPlatt wrote:Yes, that I already understood (PCR cycles), but what I want to know is how it comes about that it’s so prolific. If it’s just better at penetrating cells, then OK, that’s the spike protein at work. But if it’s replicating faster within cells, then some other genetic change has occurred, which I’ve not heard about.
GrahamPlatt wrote:Thank you Julian. However, having watched it I don’t feel the q. has been answered. Prof. Barclay describes why delta is more transmissible (it’s “stickier”, and evades our interferons by (to pinch a well-known phrase) being “oven ready” at the point of impaction). However, she does not really address (admits there is little known) about it’s other properties. As to how it produces higher viral loads then, one might imagine that because this stickiness will operate not just in the nose and throat, but also in the rest of the body, viral particles circulating in the blood stream are more likely to go on to infect the next cell in the chain, and so on. BUT, if that’s so, given that infected cells die (bursting as they release their viral parasites), a higher viral load would seem then to imply a lot more dead host cells, so why is it that these patients aren’t a whole lot sicker? Is each cell producing more virus before it burts? More virus but less cell death?
Bouleversee wrote: I opened my window wide but he didn't open his at all.
Julian wrote:heads up
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