The current policy of testing people when they’re symptomatic may miss huge numbers of cases after a study found that 86% of the people who tested positive for COVID-19 were asymptomatic.
Epidemiologists at University College London used the Office for National Statistics Infection Survey, which looks at the prevalence of COVID-19 in the community and not only those who get a test because they have symptoms.
The pilot study sampled 36,061 people living in England, Wales and Northern Ireland who were tested between 26 April and 27 June.
Of the 115 with a positive result, only 16 reported symptoms, with 99 not reporting any specific symptoms on the day of the test. Moreover, 142 people who reported symptoms on the day of the test did not test positive for COVID-19, vastly outnumbering those who tested positive.
“The fact that so many people who tested positive were asymptomatic on the day of a positive test result calls for a change to future testing strategies,” said Irene Petersen of UCL Epidemiology & Health Care.
“More widespread testing will help to capture ‘silent’ transmission and potentially prevent future outbreaks.”
The authors noted that other studies showed different results, with one in China suggesting just 5% of cases were asymptomatic, and a study in Iceland suggesting 43 cases out of 100 had no symptoms.