It is increasingly coming to light that not everyone who overcomes the coronavirus returns to a clean bill of health.
The infection is mild the vast majority of the time, however, a growing number of coronavirus survivors are enduring complications after testing negative for the infection.
Dubbed “long COVID”, the symptoms are varied and vast, affecting everything from the brain and heart to kidneys and skin.
Read more: What is long COVID?
With the coronavirus only identified at the end of 2019, long COVID is fairly mysterious, with no set diagnosis.
This makes identifying patients tricky, with doctors and officials alike somewhat in the dark about how many Britons are enduring these lingering complications.
Watch: What is long COVID?
How many people have long COVID in the UK?
Long COVID’s cause, precise symptoms and optimal treatment plan are yet to be officially laid out.
Doctors have stressed the confusion around the condition makes it tricky to identify patients, let alone help them.
The World Health Organization states most people recover from severe coronavirus symptoms within two to six weeks. Patients enduring complications beyond this time are therefore generally considered to have long COVID.
Read more: Long COVID may be four different syndromes
This definition varies, however. In August, scientists from King’s College London – who oversee the app-based COVID symptom study – said up to half a million Britons may be experiencing symptoms after supposedly overcoming the coronavirus.
In September, the same team announced around 300,000 people have complications lasting more than a month, while 60,000 are still feeling the effects of the virus over three months later.
The recent report Living with COVID19 by the UK’s National Institute for Health Research (NIHR) stressed: “We are at an early stage of understanding the disease and need to be careful not to draw conclusions prematurely.”
In an effort to better gauge the impact of long COVID, the NIHR team analysed the available evidence, which is largely restricted to small surveys.
One found more than four in five (87%) coronavirus patients who were discharged from a Rome hospital were experiencing at least one symptom 60 days after testing positive for the infection.
More than half (55%) had three or more symptoms, like fatigue, difficulty breathing, and joint or chest pain.
On 5 June, NHS England announced more than 95,000 patients were thought to have been admitted to hospitals across the country with severe coronavirus, of whom 45% were assumed to need ongoing support.
Some estimates suggest up to half (50%) of people admitted to hospital with the infection require formal rehabilitation services, it added.
Read more: Long COVID patient 'not the person she was'
It is also emerging that long COVID does not exclusively affect severe coronavirus cases, with complications also occurring among those who had a mild bout of the infection.
On 7 September, Public Health England revealed around 10% of mild coronavirus patients who were not admitted to hospital were reporting symptoms four weeks on.
To add further confusion, the NIHR team stated long COVID may in fact be made up of four syndromes: post-intensive care; post-viral fatigue; long-term COVID; and permanent organ damage.
A patient showing the signs of long COVID – for example fatigue and muscle weakness – may actually be enduring post-intensive care and post-viral fatigue syndromes.
Long COVID patients who had mild symptoms to start off with have reported particular frustration when it comes to others acknowledging their complications, which could result in many cases being missed.
Speaking of the NIHR report, author Dr Elaine Maxwell said: “This highlights the detrimental physical and psychological impact that ongoing COVID is having on many people’s lives, and how healthcare services have at times struggled to manage these new and fluctuating patterns of symptoms and problems.
“Our aim is healthcare services and staff will use this review to better understand the experiences patients have to deal with, and provide them with the access to treatment, care and support they need.
“While research is at an early stage, listening to the testimony of people living with the ongoing effects of COVID-19 provides rich insights into where we should focus future research, as well as the services we should be commissioning now.”
Medics may not be in the dark for long, however. NHS England and NHS Improvement have commissioned the National Institute for Health and Clinical Care Excellence (Nice) – a health watchdog – to develop a treatment guideline for long COVID.
The Scottish Intercollegiate Guidelines Network was given the same instruction by the chief medical officer of Scotland.
The guideline – expected by the end of 2020 – will provide a formal definition of the disease, tips on how to identify symptoms and a layout of the best treatment options to “support the management of the condition across diverse communities”.
Watch: How is coronavirus treated?