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Long Covid – Our understanding so far

2020 has pushed science to its boundaries in 2020 in a bid to understand Covid-19. While scientists around the world have risen to meet this challenge and many insights have been elucidated into both the transmission and treatment of the virus, much still remains a mystery. One salient aspect we are yet to decipher is the persistence of symptoms in a substantial subset of patients, which has been termed long Covid.

Long Covid is not yet an official medical term but over the summer and beyond it has slipped into common use. The WHO has found that a two-week period should be long enough for the virus to leave our systems, and this has of course been used as the basis for isolation periods for those infected. Long Covid is defined as the presence of symptoms beyond this two-week period.

The three symptoms we’re now all used to hearing about – a persistent cough, fever and loss of taste or smell – are often not present in long Covid cases. Instead, sufferers report a range of symptoms including chronic fatigue, muscle pain and weakness, headaches and inability to concentrate. Along with these, several mental health problems are common in long Covid cases, such as depression, anxiety and PTSD. This is complicated, however, by the fact it is unclear whether these are directly caused by the virus, a result of the uncertainty around long Covid or simply a side-effect of this tumultuous year.

It has also remained unclear why some people develop long Covid and others can be virus-free in two weeks, with many not even experiencing any symptoms. It appears non-discriminate, with even several prominent athletes experiencing it, despite being at the peak of their physical health. Notably, many young people without underlying health conditions are developing long Covid after initial infection, significantly challenging the idea that this is a dangerous or concerning virus only for the old and vulnerable.

The mechanisms behind why long Covid occurs is still relatively unknown but recent studies have provided selected insights, as well as looking at past viral outbreaks. For example, of those infected with the original 2003 SARS virus-, 25% reported long-term fatigue after the virus left their body. There are several ideas behind what can cause chronic fatigue after a viral infection, such as the immune response not returning back to normal levels or the infection continuing in another part of the body, such as the lungs or brain.

Some inflammatory molecules have been implicated, interleukin-6 and interleukin-10, which can be used to predict a person’s risk of chronic fatigue based on their levels in blood. These are also seen in those who develop severe Covid-19, so some researchers believe they are linked and at play in long Covid. Some structural and functional alterations in certain organs, such as the heart and lungs, are commonly reported in long Covid patients, and are thought to account for some symptoms.

Therefore, while more information is arising about how long Covid works and how we might approach treatment, much more work remains to be done. A major UK study called the Post-Hospitalisation COVID-19 study is recruiting 10,000 Covid-19 patients who were hospitalised with the virus and will follow them over a year to better understand the long-term consequences of the virus. More immediate action has been the setting up of a recovery help programme, where individuals can learn how to support their physical and mental health and can involve hospital investigations such as chest x-rays.

With the second wave currently hitting and the additional threat of seasonal flu, as well as the backlog of routine treatments that were postponed over the summer, the NHS is facing yet another challenge this winter. Both long-term research and shorter-term treatment of those with long Covid is pertinent to help the NHS burden. Emerging information is helping us understand the mechanisms behind the condition, which will hopefully inform potential treatments. Crucially, research is demystifying the virus that has affected all of our lives, and is turning it into a tangible challenge that can be met with science.

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