Organs affected by COVID-19

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COVID-19 is not just a respiratory disease, it affects a multitude of other organs. Beyond common cold symptoms, it can impact the heart, gastrointestinal system and cause neurological issues. There are two possible scenarios why the disease outcome is so diverse. Firstly, SARS-CoV-2 enters the cells through a receptor – angiotensin converting enzyme 2 (ACE2). ACE2 is present in most tissues, allowing the virus to infect virtually any organ. Secondly, pre-existing diseases and an abnormal immune response to the infection can lead to a life-threatening condition called cytokine storm.

By far, the respiratory system is the most commonly affected by COVID-19. Symptoms are similar to other respiratory diseases and include cough, shortness of breath, sore throat, nasal congestion and sputum production. According to MIT researchers, the cough of people who are asymptomatic may differ from healthy individuals. The human ear cannot pick up these tiny differences, but they can be detected by artificial intelligence and could open up another way to test for COVID-19.

Image: Organ specific manifestations of COVID-19.

CT scans of the chest of COVID-19 patients often reveal asymmetrically distributed dark patches. This is a sign that air in some lung spaces is replaced by fluid, causing impaired breathing. With the disease progression into a severe state, patients might experience pneumonia with acute lung injury, resulting in respiratory failure and ultimately death.

Patients with pre-existing heart conditions, such as heart failure, coronary artery disease, or cardiomyopathies are at an increased risk of developing severe COVID-19 symptoms. Moreover, cardiac issues can even occur even in asymptomatic people. A wide range of heart problems such as hypertension, myocardial injury, cardiac arrhythmia’s and acute coronary syndrome were reported after infections with  COVID-19. These symptoms can occur due to a direct effect of the virus infecting heart tissue. Indirectly, cardiac strain can happen because of a cytokine storm or respiratory failure and low oxygen levels in tissues.

One on ten patients experience gastrointestinal complications, which might arise together with, or start before respiratory symptoms. The most frequently reported are abdominal discomfort, nausea, vomiting and diarrhea. Some patients’ stool samples contain whole virus, raising the question about potential possibility of fecal transmission. Nearly half of hospitalized patients have elevated levels of liver enzymes, indicating hepatic injury. This dysfunction is likely to be due to inflammation of the liver or, in case of hospitalized patients, due to the use of hepatotoxic drugs for COVID-19 treatment.

Another organ affected by SARS-CoV-2 infection is the kidney. This poses a threat to patients on dialysis, with chronic kidney disease or renal transplantation. Complications might lead to development of acute kidney injury. This is mainly a secondary result of cytokine storms, medication (including antivirals) and pre-existing diseases, like hypertension, coagulopathy or diabetes.

Diabetes is listed as an important risk factor for COVID-19 illness, several glands can be affected by the virus. Virus infection might result in pancreatitis, its enlargement and abnormal levels of pancreatic enzymes. Moreover, SARS-CoV-2 infection might change glucose metabolism, with ketosis and ketoacidosis being the most prevalent complications.

Similar to other viral infections and chronic inflammatory diseases, in some patients COVID-19 can manifest itself through varied dermatological symptoms. The most common skin problems include a patchy rash mimicking bad sunburn, chickenpox-like lesions and hives. The majority of these issues are present on the trunk, however frostbite-like areas on toes and fingers are another particular finding.

About one-third of hospitalized patients develop ocular complications with conjunctivitis (pink eye) being most common. Viral entry receptors are present on ocular cell surfaces and entry through contamination of the tear liquid might be a potential route for SARS-CoV-2 to enter our bodies.

Mild neurological symptoms, occurring early, are common in COVID-19 patients. They include headaches and dizziness. Other warning signs of illness are changes in or loss of sense of smell and taste. This is present in nine out of ten people. Fatigue, nerve pain, skeletal muscle weakness and pain, tingling or numbness in the hands and feet can also be symptoms. In more severe cases patients experience confusion, seizures, delirium, acute cerebrovascular disease and encephalopathy. Such a broad spectrum of neurological manifestations can be explained by the SARS-CoV-2 virus entering the nervous system. After entry, viruses can cause inflammation and cytokine storms, these affect brain function and cause neuronal death. Viral particles discovered in brain autopsies and in the fluid surrounding the brain and spinal cord support this idea.

During the early stages of COVID-19 illness hematological parameters serve as indicators of disease progression. SARS-CoV-2 infection initially leads to a decrease of immune cell population (mainly lymphocytopenia) and changes in coagulation factors. The most severely affected patients are at risk of developing thrombosis, vascular dysfunction, and hemorrhagic complications.

Understanding the different mechanisms causing multi-organ injury can help to understand and manage the disease better at an early stage. This will ensure better treatment of specific patient symptoms and lead to better outcomes for patients.

References:

Chu Jennifer. “Artificial intelligence model detects asymptomatic Covid-19 infections through cellphone-recorded coughs.” MIT News. 2020

Gavriatopoulou et al. “Organ-specific manifestations of COVID-19 infection.” Clinical and Experimental Medicine. 2020

Johnson et al. “Pulmonary and Extra-Pulmonary Clinical Manifestations of COVID-19.” Frontiers in Medicine. 2020

Jain Uday. “Effect of COVID-19 on the Organs.” Cureus Journal of Medical Science. 2020

Mehta et al. “Coronavirus Disease (COVID-19): Comprehensive Review of Clinical Presentation.” Frontiers in Public Health. 2021

Thakur et al. “Multi-organ Involvement in COVID-19: Beyond Pulmonary Manifestations.” Journal of Clinical Medicine. 2021

 

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