Long covid – next global public health crisis?
Almost three years into the Covid-19 pandemic, the immediate threat of death from the disease has dropped significantly. Now, healthcare faces another problem: long covid. The condition is estimated to affect 10–30 per cent of those infected by Covid-19, and the symptoms are numerous and complex. Additionally, existing gaps in knowledge make both diagnosis and treatment difficult. In this article, BioStock reviews the current knowledge regarding symptoms and underlying causes of long covid. Tomorrow we will take a look at current treatment options and companies that are active in the field.
There is no doubt that Covid-19 has affected us in ways we have not experienced in the recent past, both on a societal and an individual level. In addition to the direct threat on our lives posed by SARS-CoV-2, it has become clear that through the consequences of long-term symptoms, another type of medical challenge has arisen. The condition, clinically named Post-Acute Sequelae of Covid-19 (PASC) and commonly known as post covid syndrome, or long covid, can be anything from mild to severely disabling. With approximately 200 million people affected worldwide, experts believe we are on the brink of the next global public health crisis.
What is long covid?
When patients previously treated for Covid-19 returned with persistent or new-onset symptoms, the medical community began to suspect that the effects of the virus extend beyond the acute phase. But what do we actually know about long covid today?
Over time, several definitions have emerged, and there is still no real consensus. However, most agree that the condition involves symptoms developed during or after an infection compatible with Covid-19, which must have lasted for more than three months and cannot be explained by an alternative diagnosis. Thus, long covid is an umbrella term – and much is still unclear. Questions remain not least about whether everyone with long covid has been affected by the same disease, or whether it actually is several different conditions with different biological causes. In addition, symptoms are alarmingly consistent with another, very complicated condition that often debuts after a viral illness – ME/CFS, or chronic fatigue syndrome, which has grim consequences for those affected.
Long covid is further complicated by the fact that it manifests itself differently in different people, and symptoms often arise from several organ systems. In total, some 200 symptoms have been linked to the condition. But even if symptoms are numerous, some are more common than others, including:
- Fatigue (excessive physical and mental tiredness that doesn’t resolve significantly with rest)
- Shortness of breath
- Cognitive dysfunction (eg, brain fog, memory problems)
- Headache/migraine
- Dysautonomia/POTS (postural orthostatic tachycardia syndrome)
- Palpitations, high resting heart rate, chest pain (often included in the above-mentioned syndrome)
- Loss or change of smell and taste
What is consistent is the fact that many patients clearly deteriorate after mental or physical exertion. In addition, the symptoms seem to fluctuate over time, and may disappear for periods only to later return.
Who is affected by long covid?
Studies show that between 10 and 30 per cent of those infected develop symptoms of long covid. Severe Covid-19 means a higher risk of prolonged symptoms, but the same type of symptoms and complications are found in people who have undergone Covid-19 with a mild illness.
It is also known that women are affected to a greater extent than men. In addition, it has been seen in several countries that long covid also affects children and young people – this despite the fact that the group has been relatively spared from Covid-19. Still, more knowledge is needed about possible differences in clinical characteristics between younger and older people.
Underlying causes
Despite everything, progress has been made and research has now begun to call on the biological explanations for long covid. Leading theories include, in no particular order: (i) consequences of organ damage caused by the virus in the acute stage, (ii) residual virus and viral antigen with consequent overactivation of the immune system, including inflammation, autoimmunity, and disruption of the microbiome. Abnormal blood markers in terms of inflammatory response have been demonstrated in patients with long covid, as well as autoimmune components that appear to be characteristic of the condition.
Another leading theory is (iii) mitochondrial dysfunction, which is believed to play a major role in long covid. Mitochondria are the cells’ powerhouses, converting energy from the food we ingest into energy necessary for our cells to function properly. Mitochondrial dysfunction can help explain why most patients suffer from fatigue, as well as worsening of symptoms following exertion – which requires more energy.
There is also strong evidence that patients with long covid suffer from (iv) endotheliopathy and micro clotting. A continuous formation of micro clots can obstruct the smallest vessels and cause a lack of oxygen in, for example, the muscles and the brain, which could explain both fatigue and pain as well as the worsening of symptoms following exertion, which places higher demands on oxygen supply.
Light at the end of the tunnel
Given the number of people affected by long covid worldwide, doctors and researchers believe that we may be facing the next global public health crisis. But even if it sounds dark, there is light at the end of the tunnel. The more pieces that are added to the biological background of long covid, the better the chances of finding treatments.
Tomorrow, BioStock will publish an article about research advancements and promising projects being conducted with the aim of diagnosing and treating long covid. Keep an eye out at biostock.se.
