Most COVID-19 cases are diagnosed before any symptoms are noticeable

Now every person with a cough or fever will be worried about COVID-19. Is it just a common cold or the pandemic infection? Scientists from UCL determined that cough, fever and other symptoms are actually poor markers of COVID-19. The truth of the matter is that 86% of people who tested positive for Covid-19 during lockdown did not have virus symptoms.

COVID-19 testing site in the UK. Image credit: Glen Wallace via Wikimedia (CC BY-SA 2.0)

Cough, sore throat, fever, loss of smell and taste – those are the common symptoms of COVID-19 infection. People who are experiencing them are encouraged to seek a test, which would verify the disease. However, most of the people who tested positive do not experience any of those symptoms. Scientists analysed data from 36,061 people living in England, Wales and Northern Ireland who were tested between 26 April and the 27 June 2020. Researchers paid attention to results of those tests as well as reported symptoms.

Just 115 people included in this study received positive test results. 158 people had COVID-19-like symptoms on the day of the test. However, just 16 people who tested positive experienced symptoms – 99 did not. This means that 86.1 % of people who tested positive experienced no COVID-19 symptoms when they were tested. This means that those symptoms that are widely published as indicators of the disease, actually are poor markers of COVID-19 infection. Absolute majority of people with confirmed COVID-19 diagnosis  were asymptomatic on the day of a positive test result, which means that some guidelines need to be adjusted.

Now people are encouraged to get tested when they are experiencing symptoms or when they had a contact with someone who tested positive. This does work for now, but these recommendations should be revised. Most COVID-19 cases are diagnosed before any symptoms are noticeable. 

Professor Andrew Phillips, co-author of the study, said: “When considering SARS-Cov-2 testing it is important to consider the purpose of the test.  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.”

It is very important to note that asymptomatic cases sometimes turn into more difficult COVID-19 cases. This happens because you may not have COVID-19 symptoms on the day of the test, but they may develop a bit later. However, scientists understand that this just means that more testing is necessary to catch more of the infections early.


Source: UCL

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