Many coronavirus patients have reported debilitating symptoms months after initially falling ill, with common “long Covid” symptoms including breathlessness, chronic fatigue and brain fog.
The reasons behind them are still unknown, scientists said.
Dr Rachael Evans, a co-investigator on a UK-wide investigation into the long-term effects of Covid-19 for patients admitted to hospital, said: “At the moment it is just so unknown.”
“We’re still very much at the point where we’re learning what the after-effects are,” he added.
“It has become very apparent that the long-term effects can happen to people that were young and fit before and perhaps had a fairly mild acute illness… enough to bring them to hospital but maybe only a day or two.”
Jade Townsend, 22, was active and sociable before she caught coronavirus, but has been left unable to work or walk more than 10 minutes from her home since symptoms began in mid-March.
Five weeks into contracting the illness, Ms Townsend was taken to hospital due to a high fever and difficulties breathing, for which she stayed overnight with antibiotics for the early stages of pneumonia.
Six months on, Ms Townsend is still suffering chronic fatigue, fevers, nausea and a fluctuating fast heart rate.
Before Covid she had been working Monday-Friday at a nursery, often waking up at 5.30am, and staying out late on weekends “doing all the typical young person things”.
“I can’t actually imagine doing that now… I’m now nearly needing more hours of sleep than time awake,” Ms Townsend, from Witney, Oxfordshire, said.
“It worries me at 22 I’ll be stuck with some of these symptoms and I won’t ever be able to get back to my normal self.”
Ms Townsend had no pre-existing conditions except a benign brain tumour which did not require her to shield and doctors have not identified as a factor in her condition.
Dr Evans, a respiratory consultant, said pneumonia patients can take up to three months to fully recover in rare cases – but Covid patients still have symptoms six months on.
“I’ve been a qualified doctor in the NHS for 23 years and I’ve not seen anything like it in respiratory medicine,” she said.
Dr Evans said understanding long Covid will ease future strains on healthcare services and wider society due to people being unable to return to work or fulfil their caring roles.
“Like with any condition, if people are left to deal with it themselves there can often become a real cycle of illness where the symptoms continue,” she added.
Dr Evans said PHOSP-Covid investigation will interview patients and assess their physical function and mental health, also taking samples to analyse their genes and immune system.
It aims to recruit 10,000 people, following them for a year in the first instance, with permission to follow them for a further 25 years from their healthcare records.
It hopes to provide an initial report from 1,000 participants’ health records within the next few months, with 4,000 more assessed through interviews and samples by the end of the year.
The ultimate goal of the research, funded through UK Research and Innovation and the National Institute for Health Research, is to find prevention and treatment methods.
“I always want to also say that there are plenty of people making a full recovery because we don’t want to cause too much concern either,” Dr Evans added.