Although these broader symptoms have been observed, in addition to the known or so-called classic symptoms of loss of smell and taste, fever and a persistent new cough, about 60 percent of infected people reported no symptoms in the week before their test, the Imperial College London conducted Real-Time Community Transmission Assessment (REACT) study unveiled on Wednesday.
“These new findings suggest that many people with COVID-19 will not be tested – and therefore will not isolate themselves – because their symptoms do not match those used in current public health guidelines to help identify infected people,” said Professor Paul Elliott, director of the REACT program at Imperial.
“We understand that there is a need for clear testing criteria and that including many symptoms commonly found in other illnesses such as seasonal flu can cause unnecessary self-isolation in people. I hope that our findings about the most informative symptoms mean that the testing can take advantage of the most up-to-date evidence, helping to identify more infected people, “he said.
Smear tests and questionnaires collected between June 2020 and January 2021 as part of the study showed that, among these other symptoms, chills, loss of appetite, headache and muscle pain were together more strongly related to the infection, alongside the four called classic symptoms.
Having any of these other symptoms or the classic ones, alone or in combination, was associated with coronavirus infection and the more symptoms people had, the more likely the test was to be positive.
The study also found that there was variation in symptoms with age. Although chills have been associated with positive tests at all ages, headaches have been reported in young people aged 5 to 17, loss of appetite in age 18 to 54 and over 55, and muscle pain in people aged 18 to 54 years . Infected children aged 5 to 17 years were also less likely to report fever, persistent cough and loss of appetite compared to adults.
The research also explored whether the emergence of the new coronavirus variant in the UK, first identified in Kent, was related to a different symptom profile. Although the symptoms were largely similar, in January of this year compared to November-December 2020, the loss or change in the sense of smell was less predictive of having COVID-19, while the proportion of people who tested positive with a new persistent cough it seemed to have increased.
“As the epidemic progresses and new variants emerge, it is essential that we continue to monitor how the virus affects people in order for testing programs to meet changing needs,” said Dr. Joshua Elliott of Imperial College School of Public Health London.
“We hope that our data will help inform the testing direction and the development of systems that can help to better identify the people who should take the COVID-19 test based on their symptoms,” he said.
Currently, people in England are encouraged to take the COVID-19 test if they experience at least one of the four classic symptoms: loss of taste, smell, fever, new persistent cough. This is called the “Pillar 2 test”.
Based on the new findings from the REACT study, the researchers estimate that the current Pillar 2 test would catch about half of all symptomatic infections if all eligible ones were tested. But if additional symptoms were included, it could be improved for three quarters of symptomatic infections.
The findings, released as a pre-printed report before being peer reviewed, are part of the ongoing flow of REACT-1 analysis, led by Imperial College London and carried out in partnership with Ipsos MORI. The Community Transmission Real-Time Assessment program is funded by the government’s Department of Health and Social Assistance.