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The beauty of the affimers is that eventually the same "strip" could have lines for Norovirus, MRSA, HPV, whatever they choose to develop.
Ophidian
@CautiousOptimist - think of i like an LFD with an unlimited amount of saliva going across it.
The LFD works because the affimers pick up the virus as it goes over them and they then travel along the strip until the little blueline dye grabs the affimer that has the virus making the positive line. The empty affimers then get grabbed by the second dye line for the proof the test worked line (very very basically). So just think of it as gallons of saliva slowly but surely carrying a virus particle to get grabbed by the affimer then hooked on the blue line. Eventually enough have got caught to make the whole line blue. - it's just a matter of time and volume across the strip. Scale that up and bingo - that's the principle of the waste water system (in my opinion).
Ophidian
Thanks Ophidian - good point! Hence my remark that this is a completely different system, so the same LoD may not apply. If I understand your suggestion rightly, the LoD would be more of an absolute number rather than a concentration, and not really comparable at all. Oh well, it was a nice thought.
I hope so, Milcait. As well/alternatively, they could install multiple detection systems on each ship, e.g. one per deck or smaller grouping of several cabins. This would give greater viral concentration with fewer positive cases, and allow them to quickly isolate affected areas.
Guys I think some of you may be misunderstanding the system here. Let's just say for arguments sake there are 10,000 virus particles in the waste water system and just for arguments sake lets say that is a million litres (I really have no idea of the actual numbers but that doesn't matter for this exemplification). If you were taking a 10ml sample to analyse (like you might for a saliva assay) then you are looking for one one thousandth of a virus particle and you're obviously not going to find it.
If you consider that is is a flow through system and think of it more like a net that catches each virus particle that goes by then it simply becomes a matter of time to detect. I virus particle every 100 litres 10 every thousand and 100 every 10,000 litres. That you would detect and knowing the flow rate and the time to detect you could work out a concentration and rom that extrapolate an infection quotient for comparisons.
Lots of at line and in line real time monitoring systems work cumulatively to give a result. That is I'm sure how this system would work.
Ophidian
Thanks Cautious.
If the waste water is to be an 'early detector' then surely it will have to detect when only a few people have virus on a cruise ship. So it must have to be ultra sensitive in my mind? Otherwise there is absolutely no point in having it if you have to wait for 10, 20 or 50 people to shed virus in order to detect it.
It must be able to detect really small virus quantities imo
Cautious optimist...Well said and itβs game set and much ..If CV can be detected in the poo in waste water, our test in your gob by comparison , is going to be a snip...Come on Avacta.LP
Nice find, thanks!
It says:
β On March 4/5, one or more gene fragments were detected in sewage of three sites, in concentrations of 2.6β30 gene copies per mL. In Amersfoort, N3 was detected in sewage 6 days before the first cases were reported. As the prevalence of COVID-19 in these cities increased in March, the RNA signal detected by each qRT-PCR assay increased, for N1βN3 up to 790β2200 gene copies per mL.β
These numbers are significantly below the average concentrations in saliva for infected people at peak viral load, but may correlate to the extremely early or late stages of infection. UK govt target production profile (TPP) analytical sensitivity (LoD) for a rapid POC Covid-19 test was 100 genome copies/ml for an excellent test; 1000 copies/ml for an acceptable test. If Avacta think they can be in the ballpark of the implied 10βs to 100βs copies/ml for a useful sewage test, that would be phenomenal.
Bearing in mind of course that this is a totally different assay format to the LFA and therefore the LoD of the two may end up quite different. Also letβs bear in mind that the concentrations in this study are for larger populations with potentially more waste dilution than on e.g. a cruise ship, so the viral concentrations may well be far lower in the measured city sewage than expected in the target markets.
If waste water is to be tested using Affimers,they must be pretty sensitive, right?
This article discusses levels of virus found.
https://pubs.acs.org/doi/10.1021/acs.estlett.0c00357
Anyone scientific know what these levels mean in terms of the sensitivity required?