Coronavirus can cause lasting lung damage – but the effects may ease over time

Antonio Guillem / Shutterstock
We know a lot about the symptoms of severe COVID-19, but relatively little about what happens when someone recovers. Could there be long-term effects? Let's take a look at what we know so far about the effects of COVID-19 on the body - especially the lungs - and the potential for permanent damage.
The lung is the organ most affected by COVID-19 with a range of serious effects. One is pneumonia, where inflammation causes the small air sacs that make up the lungs to fill with fluid. In COVID-19, pneumonia tends to affect both lungs. When large parts of the lungs are affected, people have difficulty getting enough oxygen and are hospitalized.
Another serious effect is acute respiratory distress syndrome (ARDS) - also known as "wet lung". As a result, severe inflammation quickly spreads to the lungs. People who develop this may need mechanical ventilation in an intensive care unit, sometimes for a long time.
COVID-19 has another unusual effect on the body. Compared to other respiratory viruses, it causes marked clotting in the small blood vessels of the lungs and other organs.
How the virus damages the lungs
Although the lungs can recover from heavy COVID-19, they can also suffer long-term damage of varying severity.
The SARS-CoV-2 virus enters the respiratory cells via the angiotensin converting enzyme 2 receptor (ACE2), a molecule that connects the inside of our cells to the outside via the cell membrane. In this case, some people respond to the presence of the virus by triggering an intense immune response called the "cytokine storm" and increased blood clotting, all of which damage lung cells.
Using a ventilator - which may be necessary with ARDS - can also lead to cell damage. Kiryl Lis / Shutterstock
The body replaces cells damaged by the virus with thick and stiff scar tissue. This can lead to a condition called “pulmonary fibrosis” that has been seen in people with COVID-19 and is more likely to develop when the lungs are severely affected by the infection. The disease can leave people breathless when doing activities that they would normally do without difficulty. Drugs that reduce scars can play a role in prevention.
We do not yet know how lung fibrosis affects after infection, but it can lead to long-term symptoms and a progressive decline in lung function. Therefore, it is important to pay attention to the disease in people who suffer from severe COVID-19.
However, we can examine other coronaviruses - severe acute respiratory syndrome (Sars) and Middle Eastern respiratory syndrome (Mers) - to try to predict long-term results.
We know that Sars can cause pulmonary fibrosis, and extensive analysis of Sars and Mers patients showed weakened lung function and resilience in some survivors up to six months after discharge from the hospital. However, a 15-year follow-up of the patients showed improvement in lung function and less damage that was seen with CT scans over time. An early study in people who had recovered from COVID-19 found that such damage continued to improve in the first few weeks after discharge from the hospital.
What about other organs?
COVID-19 can also cause diseases in other parts of the body, ranging from unspecific symptoms lasting several weeks to impairment of the kidneys, heart, gastrointestinal tract, nervous system and coagulation system. Some effects could be caused in part by clots in the small blood vessels that feed these organs. It is also likely that this will affect mental health.
The influence on the general fitness of a person is equally important. People who require mechanical ventilation for a long time lose a significant amount of muscle mass and remain weak after their lungs have recovered.
People with limited reserves (like the elderly) can also be deconditioned after “mild” COVID-19. This can affect their ability to live independently and therefore has an important impact on the demand for rehabilitation and social care services.
Widespread persistent lung damage could lead to more people using medical oxygen at home. Chaikom / Shutterstock
We are only six months after the first appearance of COVID-19, so it is too early to assess the extent of the long-term effects. There are still many questions. Who is most at risk of long-term effects after COVID-19? And what could prevent this? COVIDENCE UK is a research study that addresses these questions and recruits adults who have COVID-19 and haven't had to find answers.
While the vast majority who are infected with COVID-19 are fully recovering, we are likely to see more people with pulmonary fibrosis or persistent lung damage after ARDS caused by COVID-19. Many will be severely weakened for some time after a serious infection, and some will need oxygen at home. Meeting the long-term health and care needs of these people will be a major challenge.
This article is republished by The Conversation under a Creative Commons license. Read the original article.
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The authors do not work for companies or organizations that would benefit from this article, and do not consult, or receive funding from, stocks. They have not disclosed any relevant affiliations beyond their academic appointment.

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