COVID long symptoms even in people who haven't had COVID-19 🩺

Diagnosing long COVID is a risky exercise as this illness remains poorly defined.

A Canadian research team led by Professor Patrick Archambault from Université Laval demonstrates this in the journal Nature Communications, reporting that a high percentage of people who haven't had COVID-19 still exhibit characteristic symptoms of long COVID.


The research team recruited 6,723 people who had presented to the emergency room at one of the 33 participating hospitals between October 18, 2020, and February 28, 2022. "These individuals were seeking medical help for health issues not necessarily related to a respiratory infection," notes Patrick Archambault, professor in the Faculty of Medicine, researcher at VITAM Centre for Sustainable Health Research, and emergency intensive care physician at the Chaudière-Appalaches Integrated Health and Social Services Center.

The scientists divided these individuals into two groups. The first was made up of 3,933 subjects who had tested positive for COVID-19 within the 14 days preceding their emergency visit, at the time of their visit, or within 14 days after. The 2,790 other subjects, forming the control group, had also undergone a COVID-19 test during this period, but the result was negative. "Moreover, they did not have a positive COVID-19 test for the duration of their participation in the study, which lasted 6 to 12 months," adds Professor Archambault.

All these individuals were later contacted to find out if they had experienced symptoms during the first three months following their emergency room visit. According to the World Health Organization (WHO) definition, these symptoms include a distorted sense of taste, loss of smell, persistent cough, dizziness, pain, sleep disorders, difficulty concentrating, memory problems, shortness of breath, or disproportionate fatigue after physical effort.

"These symptoms must have newly appeared after a confirmed or suspected COVID-19 infection, must still be present three months after infection, must persist for at least two months, and must not be attributable to another condition," recalls Professor Archambault.

The analyses showed that 39% of people in the COVID-19 group met the diagnostic criteria for long COVID. "Doctors examining these individuals could have concluded, based on the WHO definition, that they had long COVID," the researcher estimates.

What follows is even more surprising. Nearly 21% of people who had not tested positive for COVID-19 and who did not believe they had contracted the disease also exhibited at least one symptom of long COVID. "There is a slim possibility that some of these individuals had an asymptomatic COVID-19 infection in the months following their emergency room visit," acknowledges Professor Archambault. "However, I believe this result mostly demonstrates the lack of specificity of long COVID symptoms. The outcome is that there may be an overdiagnosis of this disease."

This ambiguity could have clinical consequences, he continues. "On the one hand, people whose symptoms are wrongly attributed to long COVID might not receive the treatment appropriate for their condition. On the other hand, overdiagnosis of long COVID can hinder efforts to better understand and treat this disease. Until we have valid biomarkers for long COVID, we must continue testing during the acute phase of the disease in all individuals suspected of having COVID-19. This would avoid including in the long COVID group people who have not had COVID-19."

Other co-authors of the study published in Nature Communications affiliated with Université Laval are Martyne Audet, Matthew Menear, Éric Mercier, Jean-Sébastien Paquette, Elyse Berger Pelletier, and Sébastien Robert.