A 'Silent' Plague

Researchers at University College London have looked at the symptoms expressed by 36,000 people (presumably highly variable, in terms of age, gender, background etc) who were tested between April and June for a Covid-19 infection (https://www.theguardian.com/world/2020/oct/08/more-than-80-positive-cases-in-covid-study-had-no-core-symptoms). This was then fairly early in the pandemic, when lockdown measures were generally adhered to. Only 115 tests came back positive and, of these, fewer than 24% had any kind of symptom. Just under 14% of the sample displayed any of the 'core symptoms' (a persistent cough, a high body temperature and loss of the sense of taste/smell) of a Covid-19 infection. Although this feels like a massive study, it is really only based on the 115 positive testing individuals. They may well have been somewhat atypical of the general UK population. Having said all that, the study does suggest that asymptomatic spreaders of the virus might be relatively common. This makes it extremely difficult to do effective test and trace studies especially in notable 'hot spots' like schools, universities and food production factories. There needs to be, in some locations, regular testing of people who are showing no symptoms. Some people have suggested 'pooling' test swabs into 'batches'. Because most tests report negative findings, this would greatly speed analysis and save scarce resources. The people whose samples had been pooled, would only be individually tested when a positive batch result was generated. This would only work if a) retesting was timely and b) the 'pool' was fairly self contained. We certainly need to get a lot smarter about identfying asymptomatic transmitters.