Coronavirus survivors are 56 per cent more likely to have lasting symptoms of the infection than people who beat the flu, according to researchers trying to solve the puzzle of ‘long Covid’.
Following the initial blast of the pandemic last spring, a wave of patients came forward with lingering ailments months after clearing the virus from their bodies.
Critics said ‘long Covid’ was being overreported and questioned whether it was truly more prevalent than with other viral illnesses.
The latest Oxford University study, one of the largest of its kind to date, suggests Covid is more likely to leave sufferers debilitated than flu.
Researchers analysed the medical records of more than 270,000 Covid-positive people and compared them to 100,000 influenza patients.
They found 57 per cent of Covid patients had ‘long Covid’ symptoms up to six months later — including chest pain and fatigue.
Prolonged symptoms were also diagnosed in patients recovering from the flu, but at lower rates (42.8 per cent).
Researchers said their results suggested there was nothing ‘unique or specific’ about long Covid symptoms to Covid patients, and that people struck down by other viruses could suffer a similar array of warning signs.
The above graph shows the proportion of Covid infected patients who suffered symptoms of the virus up to three months after they cleared the infection, and three to six months after they fought off the virus
Little is known about the condition, which is yet to be rigorously defined by medics, despite the pandemic beginning more than a year ago.
But it has sparked concern because the condition can leave survivors of the virus with debilitating symptoms for months on end.
Symptoms of the condition are usually mild, however, with many sufferers only facing fatigue, shortness of breath and difficulty concentrating.
Around one in seven Covid patients still have symptoms of the virus four weeks after their initial infection, figures suggest, while one in 20 have them for more than eight weeks.
The NHS has spent more than £100million setting up clinics to help people suffering from the condition, and the UK Government has spent £20million on research.
In the study — published today in the journal PLOS Medicine — scientists combed through records of patients, most of whom lived in the US.
Only participants who tested positive for the virus were included, allowing experts to analyse the actual effects of Covid weeks after an infection.
Dozens of other studies assessing the prevalence of long Covid have also included people who merely suspected they were infected.
The Oxford-led team then checked records to see whether any of the patients had self-reported nine tell-tale symptoms of long Covid over six months after their infection, such as chest pain, abnormal breathing, diarrhoea, fatigue and headaches.
Scientists also looked through the records to unearth patients who had tested positive for flu, but not Covid, between January to December last year.
Academics then checked which patients had reported suffering any of the nine ‘long Covid’ symptoms up to six months after recovering from the diseases.
About 20 per cent of patients in the study were hospitalised with Covid, whereas eight per cent were admitted among flu patients.
The results showed Covid patients were more likely to report suffering a lingering symptom than those that caught flu.
About 57 per cent of Covid patients said they suffered at least one symptom of long Covid up to six months after they caught the virus.
And 36.5 per cent said they were still experiencing lingering symptoms between 90 and 180 days after the initial infection.
For comparison, about 42.8 per cent of flu patients said they had at least one long Covid-like symptom up to six months after they caught the virus.
And 29.7 per cent reported these symptoms between 90 to 180 days after their initial infection.
The most common long Covid symptoms for Covid patients were anxiety (15.4 per cent reported having this warning sign from 90 days after initial infection), abdominal symptoms (8.3 per cent) and abnormal breathing (7.9 per cent).
Among flu patients anxiety was also the most common symptom from 90 days after the infection began (14.3 per cent), followed by abdominal symptoms (6.8 per cent) and headaches (5.1 per cent).
Professor Paul Harrison, a psychiatrist from Oxford University who was involved in the study, said other viruses also left lingering symptoms.
He told a Science Media Centre press briefing: ‘Our data does not suggest there is anything unique or specific about long Covid symptoms yet.
‘We are simply describing what our patients are presenting to doctors with. This may be highlighting what we have ignored before.’
He added: ‘We don’t know if this is caused by one thing or several different things.
‘We don’t know how specific it is to do with Covid itself, and we don’t know what would be included under the umbrella of long Covid.
‘The list of Covid features runs into the hundreds. And the terminology is a complicated thing.’
Dr Max Taquet, a psychiatrist who led the research, added: ‘There may be long term symptoms of the flu that we did not look at before.’
Professor Masud Hussain, a neurologist who was also involved in the paper, added: ‘The data does not consider the severity of symptoms. It tells us about the incidence [how often this occurs] but not how severe the symptoms were.’