In relation to my earlier tweet regarding ct values and viral load. Since lockdown, testing rates in the UK have been incredibly high, with lots of asymptomatic screening of asymptotic people. Prevalence rates have been low across the country in general.

This testing using the ‘swab test’ detects not only acute infections, but in individuals who were acutely infected in the peak sometimes the residual RNA in cells still being cleared during the long recovery being experienced in some people. (Viruses live in cells)

We in the lab look at something flippantly thrown about as the ‘ct value’ across multiple targets on the virus genome. The higher the number the lower the amount of virus the person is likely to be excreting.

During the summer, in my lab. It was usual to see ct values above 30 and often above 35. These people were either clearing an earlier infection or were part of the sub-set of individuals who were intermittently positive following an infection months after acute infection.

Throughout lockdown, we have still seen cases who present with ct values below 30 suggesting more acute infections, but they’re not common.

In the last couple of weeks, this number of cases with ct values below 30 has increased. We’re seeing more positives overall. The feel of the authorisation queues on our systems is changing. Reminiscent of when flu returns in winter.