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Most people who test positive for coronavirus have no symptoms at the time the samples are taken, according to new research.
The data suggests that 77% of people had no symptoms on the day of the test, while 86% had none of the main warning signs: cough, temperature, or loss of taste or smell.
The results have led to warnings of “silent propagators” of COVID-19 of the scientists who worked on the study.
But some academics called for caution with the numbers, saying that people who have recovered from their symptoms or who may have them and then test positive will be counted as having no signs of the disease. coronavirus.
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The symptom research was led by Professor Irene Petersen of University College London and was based on information from the Office for National Statistics.
The study involved analyzing data from more than 36,000 people who were tested between the end of April and the end of June.
Of these, only 115 – 0.32% – tested positive for COVID-19.
Of these, 27 (23.5%) were symptomatic, while 88 (76.5%) were asymptomatic on the day of the test.
When looking at cough, fever and loss of taste / smell, seen as the main symptoms, 86.1% of those who tested positive had none of these.
Professor Peterson said that people may have had symptoms in the days leading up to the test or developed them later, but the figures suggest that large numbers may be spreading the virus while asymptomatic.
She said, “They can be silent transmitters and they don’t know it. So I think that’s a problem.
“It is possible that there are many people who are in society and do not isolate themselves because they do not know that they are positive.”
Professor Tim Spector of King’s College London, who runs the COVID Symptom Study (CSS) app, cautioned that the research does not mean that people will not have any symptoms for the duration of the infection.
He said that data from more than four million people who used the app and reported symptoms for a week found that 85% of adults reported having a fever, cough, or loss of taste or smell.
He added: “But the data on children and over 65s from the CSS application tells a different story.
“Using the three classic UK symptoms alone will lose about 50% of the cases in these important groups that were included in the ONS survey.
“In a substudy at King’s College London of twins that used antibody tests and the ability to report 20 different symptoms, we showed that only 19% of people are truly asymptomatic.
“We need to learn from other countries and improve our knowledge of all the symptoms of COVID-19 to properly control the spread of the virus.”
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Professor Paul Hunter from the University of East Anglia said the UCL study was unable to show the proportion of people with COVID who have symptoms or remain asymptomatic at some stage of their infection, as it only checks for external signs of infection when they actually took the test.
He said: “Anyone who previously had symptoms and has now recovered or is currently incubating the infection and develops symptoms within hours will not be included as symptomatic in this study.
A government spokesman said ministers aim to increase testing capacity to 500,000 a day by the end of October.
