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LONDON: Up to 90 percent of patients with COVID-19 do not display any of the three key symptoms when tested, a study published in the journal Clinical Epidemiology has found.
Scientists at University College London (UCL) revealed that in a survey, just 16 of 115 people who tested positive for COVID-19 — out of 36,000 volunteers tested between April and the end of June — had a fever, cough, or loss of taste or smell on the day their sample was taken. 
The findings suggest that global testing regimes based on developing symptoms could lead to missed cases and false diagnoses, and that many people may need to be retested frequently in the coming months.
“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 Prof. Irene Peterson, an epidemiologist at UCL.
“Future testing programs should involve frequent testing of a wider group of individuals, not just symptomatic cases, especially in high-risk settings or places where many people work or live close together such as meat factories or university halls.”
According to a South Korean study published last month, asymptomatic cases had the same amount of the virus as symptomatic ones. 
“On any given day, the majority of people with the virus will not be displaying any symptoms,” said Dr. Simon Clarke, associate professor of cellular microbiology at the University of Reading.