How long does it take to tell if a Covid case is the Delta variant? How much does it cost and how many cases are checked?
Sign up to FREE email alerts from Wales Online - The Coronavirus Briefing - your latest Welsh Covid-19 news Invalid Email Something went wrong, please try again later. Subscribe Thank you for subscribing We have more newsletters Show me See our privacy notice  The latest Public Health Wales figures suggest there are 178 confirmed cases in Wales of the Delta variant that first emerged in India. New data suggests the variant is now spreading in the community with no link to international travel and this is seen as the biggest threat as Wales emerges from the crisis because of the speed at which it spreads and concerns about vaccines being slightly less effective against it. In order to keep on top of the variants it is vital that Welsh Government decision makers are able to track which variants are circulating in Wales. WalesOnline spoke to leading PHW experts to discover how they are tracking the spread of the dangerous virus strains within Wales. This really depends on how urgent the result is. The aim in Wales is to sample every single positive result. However this isnt possible because sometimes the quality of the sample isnt there. In total we sequence somewhere between 50 and 70% of all positives from Wales, the Public Health Wales expert told WalesOnline. So we are getting most of them.  If we look at the figures for April, which is pretty consistent with other months, around 20% of samples that can be sequenced are sequenced with three days of the test been taken. That jumps to 40% within four days, about 65% within five days and 85%+ within 6 days. The numbers within seven days are 95%. This means that the vast majority of samples (that can be sequenced) will come back within a week of the swab being taken in the first place. The reason for the large jump between five days and seven days is that the labs dont work on weekends so there is a bump after five days. The PHW expert told WalesOnline: We have the ability to sequence much much faster. We have had priority cases that we do within 24-hours. Subscribe to the Wales Matters newsletter Wales Matters delivers the best of WalesOnline's coverage of politics, health, education, current affairs and local democracy straight to your inbox. Now more than ever this sort of journalism matters and we want you to be able to access it all in one place with one click. It's completely free and you can unsubscribe at any time. To subscribe, click here, enter your email address and follow the simple instructions. The cost of the process is quite complex to calculate on average because there will be sequence failures and if they get a failure they will retry it. On top of this they run negative and positive controls on each batch. They have a known sample which gets sequenced and one which is just water that is taken through the whole process to check for contamination. The PHW expert said: The per sample cost is not quite the total cost. You are talking between 40 a sample for the cost of sequencing. I would say 40 to 60. If you had no control samples and every single one went absolutely perfectly it would be 40 to 60 but it ends up being more because of the control samples.  However, if there is a requirement to do things more urgently that cost quickly rises. If we need to do things more quickly the price goes up quite a bit, they said, It's into the range of hundreds of pounds in that situation which is why we don't do that unless you have an individual who has been admitted to hospital and there is a concern that they may need to be handled differently and therefore it is time critical for us to have that information back. Once a PCR test (where your swab is sent to a lab rather than done yourself with lateral flow device) is completed, PHW teams will take the diagnostic residuals  The genetic material from those samples are then amplified up which is so effectively copied many times. In practice it is a bit like a photocopier, said a PHW expert. You take your starting material and then you put it in the photocopier and that's called a cycle. The next step is you take all the copies you have made and then make another copy of a copy. The cycle normally runs up to 40 times but by the time you get up to 30 what we find is that the genetic material is normally a bit degraded so we stop there.  That information is then put on a specialised piece of equipment called a sequencing instrument which converts the chemical nucleic acid and turns it into text made up of the letters A, C, T and G. This is all done by the pathogen genomics unit which is part of Public Health Wales. They can then compare this text (the genome) to the original Wuhan virus and work out whether it's a variant or not. The real challenge is when there is a brand new variant  Once a new variant is found experts know what to look for. It is harder to spot a brand new variant as you dont necessarily know what it will look like. The PHW expert said: We sequence many millions of copies that gives us a huge jigsaw puzzle. The reason that is really important is when you do a lateral flow test or a PCR test what you are doing is looking for a known entity. The problem with new variants emerging with the evolution of the virus is that what is important isn't what we know about, it's the mutations that we don't know about.  Lateral flow or PCR  The sequencing can be doing either using a PCR or lateral flow test. However in reality the vast majority are done following results of a PCR test because there are far more positive results and the process of conducting the PCR means that it is cheaper to sequence. This process is not only for Covid  This is also regularly conducted for diseases such as TB and HIV as well.