For most people, infection with SARS-CoV-2, the virus that causes COVID-19, produces mild short-term symptoms, acute respiratory illness, or possibly no symptoms. But some people have long-lasting symptoms after infection. This is what is called prolonged Covid.
Scientists have long investigated this variant of the disease. Although there are still dark spots, our knowledge about it is increasing. Here’s what we’ve learned so far: who is at risk, is it very common, and what its effects are.
Prolonged covid is characterized by an accumulation of symptoms, including, variably, shortness of breath, marked fatigue, headache, 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 showed that 53% were breathless one to two months later, with 34% having a cough and 69% fatigue.
In fact, initial analysis of the data sent through the COVID app suggests that 13% of people who experience covid-19 symptoms maintain them for more than 28 days, while 4% have them after more. 56 days.
Perhaps unsurprisingly, people with a more serious illness initially, characterized by more than five symptoms, seem more exposed to prolonged covid. Older age and female gender also appear to be risk factors for prolonged symptoms, as does having a higher body mass index.
Those who use the app tend to be on the fittest end of the population, and are concerned about health issues. It is therefore surprising that such a high proportion have symptoms one to two months after the initial infection. Generally, these are not people highly vulnerable to covid-19.
Other preliminary research work (pending peer review) suggests that SARS-CoV-2 could also have a long-term impact on people’s organs. But the profile of those affected in this study is different from that of those who reported symptoms through the application.
Trying to figure out what’s going on
This research, which analyzed a sample of 200 patients who had recovered from COVID-19, found mild deterioration in 32% of hearts, 33% of lungs and 12% of kidneys. And multi-organ damage was found in 25% of the patients.
The patients in this study had a mean age of 44 years, representing a significant part of the young population of working age. Only 18% had been hospitalized with covid-19, which means that organ damage can occur even after a non-serious infection. Having a disease known to lead to more serious COVID-19, such as type 2 diabetes and ischemic heart disease, was also not a prerequisite for organ damage.
There are many reasons why people may have symptoms months after a viral illness during a pandemic. But getting to the bottom of what’s going on in the body will be easier in some parts of the body than others.
When symptoms point to a specific organ, the investigation is relatively straightforward. Doctors can test the electrical flow around the heart if someone has 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 with those in his urine to measure how well the kidneys filter waste products.
The symptom of fatigue is difficult to explore
More difficult to explore is the symptom of fatigue. Another recent large-scale study has shown that this symptom is common after covid-19, occurring in more than half of the cases, and appears to be unrelated to the severity of the early disease.
Additionally, tests showed that the people tested did not have elevated levels of inflammation, suggesting that their fatigue was not caused by ongoing infection or by their immune system working overtime.
Long-lasting symptom risk factors in this study included being female, according to the covid symptoms app study, and, interestingly, having a prior diagnosis of anxiety and depression.
While men are at higher risk of serious infection, the fact that women appear to be more affected by prolonged covid may reflect a 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 in the cells of many hormone-producing organs, such as the thyroid, adrenal gland, and ovaries.
Some symptoms of long-term covid overlap with symptoms of menopause, and hormone replacement with medications may be one way to reduce the impact of symptoms. However, clinical trials will be essential to accurately determine whether this approach is safe and effective. Requests have been made to initiate such an investigation.
With so much that has happened in the last year, we will have to separate which impacts come from the virus itself and which could be the consequence of the massive social disruption brought on by this pandemic. However, what is clear is that long-term symptoms after COVID-19 are common, and that the causes and treatments of prolonged COVID will likely need to be investigated long after the outbreak has subsided.
Frances Williams, Professor of Genomic Epidemiology and Hon Consultant Rheumatologist, King’s College London
This article was originally published on The Conversation. Read the original.
