Nearly 86% of people who
tested positive for COVID-19 during the lockdown did not have any of the known
coronavirus symptoms such as cough, fever and loss of taste or smell, revealed a new UK
study on Thursday.

The University College
London (UCL) authors behind the analysis, published in ‘Clinical Epidemiology’,
concluded that a more widespread testing programme is therefore needed to catch
“silent” transmission.

“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,”
said Professor Irene Petersen, from UCL Epidemiology & Health Care.

“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,” she said.

Data
from the UK’s Office for National Statistics (ONS) Coronavirus (COVID-19)
Infection Survey pilot study — a large population-based survey looking at the
association between COVID-19 symptoms and COVID-19 test results — was used.

As per the researchers, the data showed 115 (0.32%) people out of the total 36,061 people in the pilot study had a
positive test result.

However, out of the 115, there were only 16 (13.9%) reporting COVID-19 specific symptoms (cough, and/or fever, and/or loss of taste/smell) and in contrast, 99
(86.1%) did not report any specific symptoms on the day of the test.

“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,” noted Prof Petersen.

The study also includes data on people reporting a wider range of symptoms such as fatigue and shortness of breath. Of the sample who tested positive, 27 (23.5%) were symptomatic in these aspects and 88 (76.5%) were asymptomatic on the day of the test. The authors believe the findings have significant implications for ongoing and future testing programmes.

“When considering SARS Cov 2
[Covid-19] 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,” said co-author Professor Andrew Phillips, from UCL Institute of
Global Health.

The study included data from a representative population sample of 36,061 people living in England, Wales and Northern Ireland who were tested between April 26 and June 27 and provided information on whether they had any symptoms.

Though several studies have highlighted a lower proportion of individuals
testing positive for COVID-19 are asymptomatic, the prevalence of
asymptomatic cases varies substantially, possibly due to the sampling and the
settings of the study.

For example, the study
references how among 262 confirmed cases admitted to hospitals in Beijing 13 (5%) were asymptomatic. In contrast, reports from a small village in Italy
suggest that up to 40-75% were asymptomatic.

A study of 13,000
residents in Iceland found 43 out of 100 with a positive Covid-19 test were
asymptomatic.