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How COVID-19 differs from the flu
According to a current study, the coronavirus SARS-CoV-2 damages not only the alveoli (alveoli) but also the inside of the blood vessels (endothelium), which can lead to thrombosis in small blood vessels. In addition, SARS-CoV-2 appears to trigger new vessel formation in the lungs. This newly discovered characteristic of COVID-19 clearly distinguishes the disease from the flu (influenza).
An international research team from the Brigham and Women’s Hospital in Boston and the Hannover Medical School showed that, in addition to some similarities to influenza, COVID-19 is also characterized by clear peculiarities. In particular, microthrombosis and a so-called intussusceptive neoangiogenesis, in which there are indentations in the blood vessels, appears to be significantly more common in COVID-19 than in the case of flu. The results were recently published in the renowned New England Journal of Medicine.
What was examined?
In a recent study, researchers working with thoracic surgeon Steven J. Mentzer and pathologist Danny Jonigk compared lung tissue from seven people who died from COVID-19 to seven lung tissue from people who died from infuenza A (H1N1). The tissue from ten people of the same age, who were not ill, served as the control group.
Similarities between influenza and COVID-19
The investigation uncovered some similarities between the two diseases: both are triggered by viruses, can attack the lungs and, in severe cases, cause acute lung failure, which necessitates mechanical ventilation. In both diseases, so-called alveolar damage occurs, in which the walls of the alveoli become inflamed, are covered extensively by protein deposits and thus make it difficult to supply oxygen to the blood.
COVID-19 puts a greater strain on the blood vessels than flu
However, there were also significant differences in the lungs of the patients examined, especially in connection with the blood vessels. The researchers showed that COVID-19 damaged the endothelial cells, the inner lining of the blood vessels. This increases the risk of severe endothelial damage, which can lead to blood clots and vascular growth.
Characteristic features of COVID-19
Here is an overview of the most important characteristics of COVID-19 that the research team has worked out:
- COVID-19 is a respiratory virus that can also cause blood vessel damage.
- The damage to the vascular cells could explain the often observed severe blood coagulation disorders and thrombosis or embolism.
- The damaged blood vessels can also explain other complaints related to COVID-19, such as the COVID toes, children with Kawasaki syndrome and the increased risk of stroke in COVID-19.
- The so-called intussusceptive angiogenesis, in which new blood vessels form, seems to be an attempt by the body to compensate for the damage to the vessels.
Better understanding of COVID-19
"The study improves our understanding of why lung function in SARS-CoV-2 infected people with severe disease is so severely impaired," explains Professor Jonigk. For the first time, the researchers examined the tissue samples synergistically with a very wide range of methods from micro-computed tomography, 3D electron microscopes and various molecular biological methods in order to track down the pathways of SARS-CoV-2.
The team discovered a massive number of blood clots in all sections of the blood vessels in the lungs, especially in the finest vessels, the capillaries. "These microthrombi block the fine pulmonary vessels and thus additionally increase the patient's shortness of breath," emphasizes the pathologist. This phenomenon also exists in severely damaged lungs after influenza infections, but to a much lesser extent.
What is intususceptive neoangiogenesis?
Particularly noticeable was the occurrence of intussusceptive neoangiogenesis, which has not yet been described in the context of diffuse alveolar damage and which "distinguishes COVID-19 fundamentally from comparable severe lung infections caused by influenza viruses", says Jonigk. This process results in indentations in the lumen of the vessel. The body is trying to split an existing blood vessel into two parts.
COVID-19: three main changes in the lungs
"The three changes in the lungs in SARS-CoV-2 infections that were comprehensively described for the first time in our study are the massive damage to the blood vessels, the excessive blood clotting with constipation of the finest lung vessels and the formation of new vessels, which is characteristic of COVID-19," summarizes the professor of pathology.
Another piece of the puzzle has been added to the decryption of COVID-19. This study highlights the need for further research that looks at the angiogenesis and vascular effects of COVID-19 to derive potential therapies. (vb)
Author and source information
This text corresponds to the requirements of the medical literature, medical guidelines and current studies and has been checked by medical doctors.
Graduate editor (FH) Volker Blasek
- Maximilian Ackermann, Stijn E. Verleden, Mark Kuehnel, et al .: Pulmonary Vascular Endothelialitis, Thrombosis, and Angiogenesis in Covid-19; in: NEJM, 2020, nejm.org
- Hannover Medical School: How the coronavirus damages the lungs (published: May 22, 2020), corona.mhh.de
- Brigham and Women's Hospital: Lungs of deceased COVID-19 patients show distinctive features (released May 21, 2020), eurekalert.org