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expert reaction to latest NHS Test and Trace figures

NHS Test and Trace have released the latest figures for UK contact tracing, for the week of 27 August to 2 September.


Prof James Naismith FRS FMedSci, Director of the Rosalind Franklin Institute, and Professor of Structural Biology, University of Oxford, said:

“Today’s track and trace digest is consistent with the news from elsewhere. It seems clear that there is now a real increase in the number of people infected with covid19; it is not just more testing. The daily positive test counts do not seem to fit a natural pattern, suggesting reporting delays in the system. We are nowhere near the exponential growth seen in March, but the virus is building; this is worrying given winter is coming. It will be important to see the ONS survey tomorrow, but as I and others have noted, this does lag the real time data. 

“It is disappointing that satellite test centre delays are growing, this suggests that this part of the testing system is starting to show very significant strain. Information is only useful if it is rapid enough to do good, if it cannot be fixed, the resource may be better employed elsewhere.

“In terms of tracing, the number of people transferred to the tracing system grew by 16 % whilst the performance remained stable, a good sign. However, 16 % is less than the 43 % jump in the number of positive cases, obviously next week we must see a large jump in people entering tracing.

“The report is silent on measures to support isolation. The whole point of the system is for sick people to stay away from the well, thus breaking the chain of infection.

“Testing capacity (2.5 million per week) is now much higher than the number of tests processed (1.3 million per week). There seems to be no lack of demand for testing, so this is a puzzle. It would be useful if the government will explain how it defines capacity. In a chemical reaction, there are many steps, the overall rate of the reaction that we care about, is determined by the slowest step; it does not matter if all the other steps are much much faster. The most useful measure of testing capacity covers the whole process, from booking tests, arriving at the test site, swabbing, transporting swabs, prepping swabs, running the PCR test, reading out the results, reporting the results and informing the patient.”


Dr Daniel Lawson, Lecturer in Statistical Science, School of Mathematics, University of Bristol said: 

“There is now no doubt that cases are growing. Because growth is exponential, the number of new cases will continue to rise rapidly, until our actions prevent this. The government has already acted, but the delay in the infection process, and generating data reports, mean it will be hard to know whether infection rate is controlled by this action until potentially too late. We must get the infection number per infection (R number) below one to prevent a large second wave which will be impossible to prevent reaching vulnerable populations.

“Proper widespread testing – not just of suspected cases but of the general population – is key to catching outbreaks before they get out of control, though may be being implemented too late.

“Track and trace is also important. Although testing time at testing centres and mobile testing units is stable, home test kits and satellite test centres are dangerously slow – taking over 3 days on average – which will prevent proper test and trace response. Track and trace itself continues with little change in performance, though the numbers should be watched carefully in case the system becomes strained as cases rise.”



All our previous output on this subject can be seen at this weblink:


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