COVID-19 may have a wider set of symptoms than previously thought, according a large UK study. Factoring four of these symptoms into decisions on who gets tested has a big impact on detection efforts, the investigators say.

In addition to the four classic COVID-19 symptoms — loss of sense of smell and taste, fever and new persistent cough — a wide range of other symptoms exist, an analysis of data from more than one million people revealed. Among these, a combined set of chills, loss of appetite, headache and muscle aches were the most strongly linked with SARS-CoV-2 infection.

The more of these symptoms a participant had, the greater their likelihood of testing positive for COVID-19 on a polymerase reaction test, reported the authors in a working paper published Feb. 10. When looking at symptoms singly, chills were associated with testing positive in people of all ages, and appetite loss was a notably strong sign of infection in people aged 55 years and older (along with people aged 18 to 54).

In England, testing by PCR (molecular) test is reserved for people who exhibit one of the four classic COVID-19 symptoms. Based on the new findings, the researchers estimate that this system would pick up about half of all symptomatic infections if everyone eligible were tested. But if the lesser-known symptoms were included, testing would detect fully three-quarters of symptomatic infections, they said.

“These new findings suggest many people with COVID-19 won’t be getting tested — and therefore won’t be self-isolating — because their symptoms don’t match those used in current public health guidance to help identify infected people,” said lead author Paul Elliott, MBBS, Ph.D., of Imperial College London.

The findings also confirmed the prevalence of asymptomatic COVID-19, highlighting the difficulties encountered in slowing the spread of the virus. Fully 60% of people did not report experiencing any symptoms in the week leading up to their test.

Data came from swab tests and questionnaires collected between June 2020 and January 2021 in the Imperial College London-led REACT study.