What's the problem?
Most people who are infected with COVID-19 suffer little more than a persistent cough, high temperature or a loss of taste and smell before recovering within a couple of weeks – but an increasing number of people are facing a longer and more serious battle.
A report by the World Health Organization (WHO) has found that 5 to 20 percent of people who are infected with COVID-19 are still ill after four weeks, while one in 10 remains sick after 12 weeks. Many suffer from an overlapping combination of debilitating symptoms and could face long-term disability. This condition is classified as Long COVID-19.
Suffers have reported a range of symptoms, including heart palpitations, extreme fatigue, neurological problems, chest and muscle pain, thrombosis and even autoimmunity, in which the immune system mistakenly attacks healthy cells rather than the virus. At present there is no universal diagnosis of Long COVID-19 but there is growing evidence of those most at risk.
READ MORE
How well are COVID-19 vaccines working?
China's Two Sessions at a glance
The woman fighting for equality in Russia
In the UK, the COVID Symptom Study based at King's College London, recruited 4 million people who report COVID-19 symptoms and test results on an app. It found the strongest predictors of persistent symptoms were increasing age, followed by the number of symptoms in the early stage of illness. Females, asthmatics and people with a high body mass index (BMI) were other risk groups.
The WHO report also revealed that developing symptomatic Long COVID-19 isn't dependent on the severity of the initial COVID-19 infection or the duration of symptoms associated with it. A study in Germany revealed large numbers of people have developed Long COVID-19 despite not requiring hospital treatment for their initial illness.
Most people who catch COVID-19 suffer minor symptoms and recover in just a couple of weeks but a growing number of people are still ill after 12 weeks. /AFP
What's the worst that can happen?
The end of the pandemic is potentially in sight for Europe's richest nations as they roll out vaccines en masse and case numbers begin to fall. But they could face a hangover if they fail to find out why people suffer with Long COVID-19 and how to help them recover.
So far, most countries have failed to formulate a strategy to combat the condition. The WHO says that aside from in the UK, patients in Europe have no access to widespread specialist Long COVID-19 treatment, meaning most have been left in a perpetual state of illness with no sign of a solution.
While all European countries have implemented effective data monitoring to record metrics such as the number of daily cases of COVID-19 and deaths there is currently no such surveillance in place for Long COVID-19. The WHO says this must be the starting point for nations to develop a plan to deal with the condition.
Long COVID-19 has left many people unable to work. While the elderly appear to be most at risk of developing the condition, it has also affected a significant number of younger people, who are part of the nation's workforce and contribute to a strong economy.
Those who are unable to work for long periods could potentially lose their jobs, resulting in increasing levels of unemployment. Healthcare services also face being overwhelmed as resources are required to treat Long COVID-19 sufferers away from hospitals on an ongoing basis.
Now, the WHO has urged politicians to work with scientists, healthcare experts and Long COVID-19 sufferers to form robust strategies to deal with the condition or face a costly and long-term battle to rehabilitate people in the months and years ahead.
A nurse prepares to administer a Pfizer vaccine in the UK, where there is hope vaccines could bring an end the worst of the pandemic. But health experts are warning of a 'pandemic after the pandemic.' /AFP
What do the experts say?
In the UK, the Office for National Statistics has estimated that 150,000 people are currently suffering from Long COVID-19 in England, Scotland, Wales and Northern Ireland.
One of those people is Nathalie MacDermott, 38, an infectious diseases expert with experience in helping countries across Asia and Africa to deal with epidemics.
Since the start of the pandemic, MacDermott has developed another area of expertise in Long COVID-19 as a result of her nearly year-long battle with the condition.
After contracting the virus in March 2020, she recovered and returned to work within 10 days but believes she was reinfected in May. Since then, she has suffered a range of serious health problems that have limited her ability to work and socialize.
She told CGTN: "I find it quite difficult to walk now further than about 200 meters unless I'm using crutches and I have some ongoing problems with my bladder and my bowel and things like that. The neurologists think that I have some sort of damage to my spinal cord [caused by the virus], but it's not clearly showing up on our standard imaging. So it's not exactly clear what's going on."
More worrying for MacDermott is that her symptoms aren't improving. She added: "They are sort of gradually deteriorating, so every few weeks I'll develop a couple of days of fever for some reason. And then I will discover shortly after that I've lost sensation in another part of my body or that something's just not working as well as it was."
Access to healthcare services has also proved difficult, with hospitals overwhelmed with people fighting COVID-19. They are also limited in the help they can administer. "There isn't any funding into proper clinical trials yet," she explained. "Some of that's because of the limitations in understanding exactly what's going on and needing to define the condition before we can launch into clinical trials.
"I think we need to pick up some pace, because this is probably going to be the pandemic that follows the pandemic, if you see what I mean, in terms of the number of people affected and the challenges of addressing that in a health system that's already behind."