The ‘silent transmission’ of COVID-19 is of huge concern as researchers have found nearly 90% of people with the condition do not have the symptoms.
People who have a persistent cough, high temperature and lose their sense of smell or taste are being told to stay home to protect other people and stop the spread.
However, a team from the University College London (UCL) say that health data recorded between April and June showed that only 16 who tested positive for coronavirus out of 115 had any of those symptoms.
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When fatigue and shortness of breath were added to the ‘core’ symptoms list, just 23% of those people in the study had the warning signs.
What the study did show is that 158 people had at least one of the three tell-tale symptoms when they were swabbed for the virus, but only 10% actually tested positive.
Lead author Professor Irene Petersen (UCL Epidemiology & Health Care) said: “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. More widespread testing will help to capture “silent” transmission and potentially prevent future outbreaks.
“Future testing programmes 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. In the case of university halls, it may be particularly relevant to test all students before they go home for Christmas.
“Pooled testing could be one way to help implement a widespread testing strategy where several tests are pooled together in one analysis to save time and resources on individual testing. This strategy would be an efficient way to test when the overall prevalence is low as negative pooled samples can quickly show a large group of people are not infectious.”
Co-author Professor Andrew Phillips, from UCL’s Institute of Global Health, added: “When considering SARS Cov 2 testing it is important to consider the purpose of the test.
In the community:
“A test done to indicate whether a person currently has virus levels that are likely to mean they are infectious, and not to rule in or rule out any presence of virus, does not require such a high sensitivity and cheaper rapid tests are more feasible. “
The findings of the study have been published in the Clinical Epidemiology journal.