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For most people, infection with SARS-CoV-2 – the virus that causes COVID-19 – results in mild, short-term symptoms, acute respiratory illness, or perhaps no symptoms. But some people have lasting symptoms after their infection – this has been called “long COVID”.
Scientists are still looking for COVID for a long time. This is not well understood, although our knowledge about it is increasing. Here I take a look at what we’ve learned about it so far – who is at risk, how common it is, and what its effects are.
By defining who is at risk for a long COVID and the mechanisms involved, we can reveal appropriate treatments to try – or if steps taken early in the course of the disease could improve it.
Great vulnerability
Long-term COVID is characterized by a constellation of symptoms, including – variably – shortness of breath, marked fatigue, headaches, and loss of the ability to taste and smell normally.
A relatively large study of 384 people sick enough to be admitted to hospital with COVID-19 found that 53% remained short of breath on a follow-up assessment one to two months later, with 34% having a cough and 69 % tiredness.
Indeed, an early analysis of self-reported data submitted through the COVID Symptom Study app suggests that 13% of people who show symptoms of COVID-19 have had it for more than 28 days, while 4% show symptoms after more than 56 days.
Unsurprisingly, people initially with more serious illness – characterized by more than five symptoms – appear to be at increased risk of long-term COVID. Older age and being female also appear to be risk factors for prolonged symptoms, as does a higher body mass index.
Those who use the app tend to be the fittest of the population, with an interest in health issues. It is therefore surprising that such a high proportion have symptoms one to two months after the initial infection. In general, these are not very vulnerable people to COVID-19.
Another piece of early research (pending peer review) suggests that SARS-CoV-2 could have a long-term impact on human organs as well. But the profile of those affected in this study is different from those who report symptoms through the app.
This research, which looked at a sample of 200 patients who had recovered from COVID-19, found slight organ damage in 32% of people’s hearts, 33% of lungs and 12% of kidneys. Multiple organ damage was found in 25% of patients.
The patients in this study had an average age of 44 years and were therefore largely part of the young population of working age. Only 18 percent had been hospitalized for COVID-19, meaning organ damage can occur even after a non-severe infection. Having an illness known to lead to more severe COVID-19, like type 2 diabetes and ischemic heart disease, was also not a prerequisite for organ damage.
Find out what’s going on
There are many reasons why people can show symptoms months after viral illness during a pandemic. But getting to the bottom of what’s going on inside people will be easier for some parts of the body than for others.
When symptoms point to a specific organ, investigation is relatively straightforward. Clinicians can examine the electrical flow around the heart if someone is suffering from palpitations. Or they can study lung function – tissue elasticity and gas exchange – where shortness of breath is the predominant symptom.
To determine if kidney function has deteriorated, the components of a patient’s blood plasma are compared to those of their urine to measure the efficiency of the filtration of waste by the kidneys.
The symptom of fatigue is more difficult to explore. Another recent large-scale study showed that this symptom is common after COVID-19 – occurring in more than half of cases – and appears unrelated to the severity of early illness.
Additionally, tests showed that those examined did not have high levels of inflammation, suggesting that their fatigue was not caused by continued infection or extra work on their immune system.
Long-term symptom risk factors in this study included being female – according to the COVID Symptom App study – and, interestingly, having a previous diagnosis of anxiety and depression.
While men are at increased risk of serious infection, the fact that women seem to be more affected by a long-term COVID may reflect their different or changing hormonal status. The ACE2 receptor that SARS-CoV-2 uses to infect the body is found not only on the surface of respiratory cells, but also on cells of many organs that produce hormones, including the thyroid, adrenal gland, and ovaries.
Some symptoms of prolonged COVID overlap with symptoms of menopause, and hormone replacement with medication may be a way to reduce the impact of symptoms. However, clinical trials will be essential to accurately determine whether this approach is both safe and effective. Requests to launch such research have been made.
With so much that has happened in the past year, we will need to distinguish which impacts stem from the virus itself versus those which could be the result of the massive social disruption caused by this pandemic.
What is clear, however, is that long-term symptoms after COVID-19 are common, and research into the causes and treatments for long-term COVID will likely be needed long after the outbreak itself has subsided. .
Frances Williams, Professor of Genomic Epidemiology and Honorable Consultant Rheumatologist, King’s College London.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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