For most people, infection with SARS-CoV-2 – the virus that causes COVID-19 – leads to mild, short-term symptoms, acute respiratory illness or probably no symptoms. But some people have long-lasting symptoms after their infection – this has been dubbed “long COVID”.
Scientists are still researching COVID for a long time. It is not well understood, although our knowledge of it is growing. Here I take a look at what I’ve learned about it so far – who is at risk, how common it is and what its effects are.
To define who is at risk for long-term COVID and the mechanisms involved, we can disclose appropriate treatments to try – or whether measures taken early in the course of the disease could improve it.
Wide vulnerability
Long COVID is characterized by a constellation of symptoms, including – variably – difficulty breathing, marked fatigue, headache and loss of ability to taste and smell normally.
A relatively large study of 384 people sick enough to be hospitalized with COVID-19 showed that 53 percent were out of breath at a follow-up assessment one or two months later, with 34 percent having a cough and 69 percent. percent reporting fatigue.
Indeed, early analysis of self-reported data transmitted via the COVID Symptom Study suggests that 13% of people with COVID-19 symptoms have them for more than 28 days, while 4% have symptoms after more than 28 days. 56 days.
Perhaps surprisingly, people with a more severe disease initially – characterized by more than five symptoms – appear to have an increased risk of long-term COVID. Older age and woman are also risk factors for prolonged symptoms, as is a higher body mass index.
Those who use the app tend to be at the more appropriate end of the population, with an interest in health issues. So, it is surprising that such a large proportion has symptoms one or two months after the initial infection. In general, they are not extremely vulnerable to COVID-19.
Another 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 is different from those who report symptoms through the app.
This research, which looked at a sample of 200 patients who recovered from COVID-19, found mild organ damage in 32% of people’s hearts, 33% of people’s lungs and 12% of people’s kidneys. Multiple organ damage was found in 25% of patients.
The patients in this study had a mean age of 44 years, so they were part of the young, working-age population. Only 18% were hospitalized with COVID-19, which means that organ damage can occur even after a non-severe infection. Having a disease known to lead to more severe COVID-19, such as type 2 diabetes and ischemic heart disease, was not a prerequisite for organ damage.
Finding out what’s going on
There are many reasons why people may experience symptoms a few months after a viral illness during a pandemic. But getting to the bottom of what is going on inside people will be easier for some parts of the body than for others.
Where symptoms indicate a particular organ, the investigation is relatively simple. Clinicians can examine the flow of electricity around the heart if someone is throbbing. 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 in the urine to measure how well the kidneys are filtering waste.
Rather more difficult to explore 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 cases – and does not seem to be related to the severity of early disease.
Moreover, the tests showed that the people examined did not have high levels of inflammation, suggesting that their fatigue was not caused by the continuous infection or the immune system working overtime.
Risk factors for long-term symptoms in this study included being a woman – consistent with the COVID Symptom App study – and, interestingly, having a previous diagnosis of anxiety and depression.
While men have an increased risk of severe infection, women appear to be more affected by long-term COVID may reflect their different or changing hormonal status. The ACE2 receptor that SARS-CoV-2 uses to infect the body is present not only on the surface of respiratory cells, but also on the cells of many hormone-producing organs, including the thyroid, adrenal gland and ovaries.
Some symptoms of prolonged COVID overlap with menopausal symptoms and hormone replacement using medications may be a way to reduce the impact of symptoms. However, clinical trials will be essential to determine exactly whether this approach is both safe and effective. Applications have been submitted for the launch of such research.
With so many events in the last year, we will have to eliminate the impact that comes from the virus itself and which could be the consequence of the massive social disruption caused by this pandemic.
What is clear, however, is that long-term symptoms after COVID-19 are common and that research into the causes and treatments of long COVID will probably be needed long after the outbreak itself has disappeared.
Frances Williams, Professor of Genomic Epidemiology and Rheumatologist Consultant, King’s College London.
This article is republished from Conversation under a Creative Commons license. Read the original article.