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What happens to the lungs when infected by COVID-19?


COVID-19, short for Coronavirus Disease 2019, is no longer a stranger to anyone. This incredibly infectious disease that was first detected in a cluster of unknown pneumonia cases in Wuhan, China had caused devastating impacts globally. In just a few months’ time, nations grappled with the COVID-19 pandemic. Since the increase of coronavirus testing, there have been more than five million confirmed cases worldwide. COVID-19 is a viral infection of the respiratory system caused by a novel coronavirus, designated as SARS-CoV-2. You may find SARS-CoV-2 familiar because the virus is actually from the same family of coronaviruses that had caused the outbreaks of SARS and MERS back in 2002 and 2012 respectively. Despite having two previous outbreaks by the same family of virus, researches on developing a successful vaccine did not manage to be completed. Presently, no vaccine or effective treatment is available against COVID-19. Patients infected with COVID-19 had to rely on their immune systems to fight the virus, with some receiving supportive treatments such as hydration and ventilation. However, not all patients develop severe disease and need ventilatory support. In a report from the Chinese Center for Disease Control and Prevention, as much as 81% of cases were reported to be mild, or with no pneumonia. Their symptoms include fever, cough, fatigue, sore throat, diarrhea, loss of appetite, loss of smell and lack of taste. Only 14% developed severe disease (with hypoxia or shortness of breath) and 5% with critical disease (with respiratory failure, shock or multiorgan dysfunction). Moreover, the fatality rate of COVID-19 seems to be lower than SARS and MERS, accounting only 3.4%. In other words, most patients recover from COVID-19. Nonetheless, preventive measures should not be taken lightly as experts found that it can cause long lasting problems to the lungs even after recovery.

So what exactly happens to the lungs when a person is infected with COVID-19? An individual is said to be infected when the virus managed to enter the human cell and hijacked it to make more copies of itself. Cells that are mainly targeted by the virus are the lining of the respiratory tree which consists of the bronchus, bronchioles and alveoli. These cells are important in ensuring an effective respiration, especially the alveoli which act like tiny air sacs in the lungs. It functions as a site for gas exchange where carbon dioxide is released and oxygen is absorbed. However, in COVID-19, the virus damages the alveoli and the cell linings, compromising the exchange of gas. As a result, the levels of oxygen in the bloodstream fall, causing hypoxia, a low-oxygen state in the body that damages organs and is potentially life threatening. At the same time, the cell death caused by the virus triggers the immune system. Soon enough, the lungs are filled with white blood cells trying to get rid of the virus and the infected cells. Since it is a new virus, the elimination of the virus takes longer as the body has to recognise it and create new antibodies. Furthermore, there is evidence that the COVID-19 virus has the ability to stimulate a cytokine storm, which is a sudden surge of chemical signals released in the body, causing the immune system to respond aggressively. All of these cause pneumonia, in which the lungs are filled with fluid and inflammation, leading to breathing difficulties. For some, the breathing problems are so severe that they require oxygen therapy or a ventilator. To make matters worse, the pneumonia that COVID-19 causes tends to take hold in both lungs, as compared to the typical pneumonia that only affect one part of the lungs. This explains why symptoms of COVID-19 are more severe as both lungs are limited in their ability to take in oxygen. While most people recover from typical pneumonia without any lasting lung damage, the lung injury caused by the pneumonia associated with COVID-19 is severe and might take months to improve.

As COVID-19 pneumonia progresses, more and more alveoli become filled with fluid leaking from the tiny blood vessels in the lungs. Eventually, shortness of breath sets in, and this ultimately leads to acute respiratory distress syndrome (ARDS), a form of lung failure. Patients with ARDS typically are unable to breath on their own and often require ventilatory support to help circulate oxygen in the body. ARDS is fatal whether it occurs at home or at the hospital. Patients who survive ARDS and recover from COVID-19 may have long lasting scarring in the lungs.

Besides, COVID-19 can also cause sepsis and superinfection. Sepsis occurs when an infection enters and spreads through the bloodstream, causing damage all over the body and destroying multiple organs. Patients may succumb to multiorgan failure, and if recover, have a lasting damage to the lungs and other organs. Also, the immune system that is so occupied with COVID-19 leaves the body vulnerable to infection by other bacteria or viruses on top of the COVID-19 – a superinfection. More infections can cause additional damage to the lungs and result in more scarring. However, you can always consult about the symptoms with your doctors before heading for COVID test.