For most people, infection with SARS-CoV-2 – the virus that causes COVID-19 – leads to mild, short-term symptoms, acute respiratory distress or possibly no symptoms at all. But some people have long-lasting symptoms after their infection – this is called ‘long COVID’.
Scientists are still investigating COVID for a long time. It is not well understood, although our knowledge of it is growing. Here I look at what we have learned so far – who is at risk, how common it is and what the consequences are.
To determine who is at risk of long-term COVID and the mechanisms involved, we can reveal appropriate treatments to try – or the steps taken early in the course of the disease can improve it.
Broad vulnerability
Long COVID is characterized by a constellation of symptoms, including – variable – shortness of breath, marked fatigue, headache and loss of the ability to taste and smell normally.
A relatively large study among 384 individuals who were ill enough to be admitted to the hospital with COVID-19 showed that 53 percent remained breathless one to two months later during a follow-up assessment, with 34 percent coughing and 69 percent having fatigue reported.
In contrast, early analysis of self-reported data submitted through the COVID symptom study app indicates that 13 percent of people experiencing COVID-19 symptoms have it for longer than 28 days, while 4 percent after more than 56 days have symptoms.
Perhaps unsurprisingly, people with a worse disease initially – characterized by more than five symptoms – appear to be at increased risk for long-term COVID. Age and womanhood also appear to be risk factors for long-term symptoms, as well as a higher body mass index.
Those who use the app tend to be at the fitter end of the population, with an interest in health issues. It is therefore surprising that such a large percentage have symptoms one to two months after the initial infection. In general, these are not people who are very vulnerable to COVID-19.
A little more early research (pending peer review) suggests that SARS-CoV-2 may also have a long-term impact on human organs. But the profile of those affected in this study differs from those who report symptoms via the app.
This study, which looked at a sample of 200 patients recovering from COVID-19, found mild organ weakness in 32 percent of people’s hearts, 33 percent of people’s lungs and 12 percent of people’s kidneys. is. Several organ damage was found in 25 percent of the patients.
Patients in this study had a mean age of 44 years, so they were very much part of the young working-age population. Only 18 percent were hospitalized with COVID-19, meaning organ damage can occur even after a non-serious infection. Nor was it a prerequisite for organ damage to have a disease that leads to worse COVID-19, such as type 2 diabetes and ischemic heart disease.
Find out what’s going on
There are many reasons why people may have symptoms during a pandemic months after a viral illness. But it will be easier for some body parts to look at the bottom of what is going on inside people than others.
Where symptoms indicate a specific organ, examination is relatively simple. 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 the kidney function has deteriorated, components in a patient’s blood plasma are compared with those in their urine to measure how well the kidneys filter waste products.
Another more difficult examination is the symptom of fatigue. Another recent large-scale study showed that this symptom is common after COVID-19 – which occurs in more than half of the cases – and that it is not related to the severity of the early disease.
What’s more, tests have shown that the people examined have no elevated levels of inflammation, indicating that their fatigue was not caused by continued infection or that their immune system was working overtime.
Risk factors for chronic symptoms in this study include that I am female – consistent with the study of the COVID symptom app – and, interestingly, a previous diagnosis of anxiety and depression.
While men are at increased risk for serious infection, women may appear to be more affected by long COVID, which may reflect their different or changing hormone statuses. The ACE2 receptor that uses SARS-CoV-2 to infect the body is not only on the surface of respiratory cells but also in the cells of many organs that produce hormones including the thyroid gland, adrenal glands and ovaries.
Some symptoms of long COVID overlap with menopausal symptoms, and hormone replacement by medication may be one way to reduce the impact of symptoms. However, clinical trials will be necessary to accurately determine whether this approach is safe and effective. Applications have been made to launch such research.
Since so much has happened in the past year, we will have to tease the effects of the virus itself, and what could be the result of the great social disruption this pandemic is causing.
What is clear, however, is that long-term symptoms after COVID-19 are common, and that research into the causes and treatment of long COVID is likely to be necessary long after the outbreak itself has subsided.
Frances Williams, Professor of Genomic Epidemiology and Rheumatologist, King’s College London.
This article was published from The Conversation under a Creative Commons license. Read the original article.