COVID -19: Frequently asked questions and some basic facts (8)
DR SHYAMKUMAR LAISHRAM
Q. 22. How the SARS – CoV – 2 causes illness of COVID – 19?
Ans. SARS – CoV – 2 virus once it enters the body, it starts infecting mucosa of the upper respiratory tract including nose, mouth, naso-pharynx, larynx and large respiratory tract called trachea and bronchus. These cells have large numbers of receptors known as ACE- 2 (angiotensin converting enzyme – 2) receptors on their surfaces. ACE – 2 has a big role in regulating blood pressure. Cell receptors play a key role in passing chemicals into cells and in triggering signals between cells. SARS – CoV – 2 has a surface protein that is primed to lock on ACE-2 receptor and penetrating the cell slips it’s RNA into the cell. Once it enters inside the host cell, it’s RNA inserts itself into the cell’s own replication machinery and begins to replicate itself into multiple copies of the virus until it kills the cell by bursting. After this these new viruses spread down infection by attaching to the ACE – 2 receptors in the surrounding cells. Antibodies generated by the body’s immune system eventually target the virus and it most cases halts it’s progress. At this period of time, the patient begins to experience mild version of symptoms like dry cough, fever, shortness of breath and headache and muscle pain and tiredness compatible with flu.
As the viruses continue infection of the surrounding epithelial cells and go down the lower respiratory tract, epithelium of the smallest and terminal parts of the respiratory tract called bronchioles lined with ACE – 2 rich epithelial lining cells re-infected and killed in the same way as above. These bronchioles are ended in the tiny air sacs called alveoli in the lungs. Smallest of the arteries called arterioles and capillaries are running along the wall of the alveoli where the lungs and bloodstream exchange oxygen from the air and carbon dioxide from these alveoli are lined with exceedingly thin epithelium that are rich in ACE -2 receptors. These epithelial cells are killed as in the upper respiratory tract, doe to body’s immune reaction there is accumulation of fluids, pus, and killed cells and the bronchioles are blocked and the alveoli are solidified and due to these there is no exchange of oxygen from air with carbon-dioxide in the air leading to severe difficulty in respiration and shortness of breath and respiratory failure. There is lowering of oxygen and increasing of carbon-dioxide levels in blood. Due to severe hypoxia (low oxygen in blood) all the organs are damaged causing multi-organ failure and death.
Enterocytes of gastro-intestinal tracts tract are also rich in ACE- 2 receptors. Probably the virus enters mostly through respiratory tract. Kidney is also rich in ACE – 2 receptors and there is injury to kidney. There is also inflammation of cardiac muscles (myocarditis) and cardiac arrest. The endothelial lining of arteries and veins in all the organs are rich in ACE -2 receptors. So, there is possibility that every organ can be infected.
Q. 23. What are the percentages of clinical signs and symptoms in COVID -19 patients?
Ans. Though the commonest findings in COVID- 19 patients fever, cough and breathing difficulties and shortness of breath, there are other findings. Just to have a glimpse of the clinical feature the following table is given.
Q. 24. How long the corona virus survives in the environment?
Ans. As SARS – CoV-2 virus is a novel virus, many researchers are trying to find the longevity of the virus in different situations. There are frequent changes in the longevity of this virus.
Studies have also found that cloth, porous surfaces and paper have less days of survival due to faster drying. Wooden surface if polished has longer life span. Survival in blood and faecal matter are under investigation. The infectivity from a COVID – 19 deceased person’s body , though found not infective in some findings, as how long the virus survives in blood is not known and as well how long the virus survive in the respiratory secretions (though not droplets or aerosol) is not known, there is risk of having infection. Whatever may be in all the situations physical distance, proper hand washing with soap and water or hand sanitization with alcohol (at least 60%), proper disposal of soiled cloths, cleaning of rooms and surfaces and proper performing of funerals and last rites are all to be done strictly following guidelines given by MOHFW, GOI, ICMR, WHO, CDC etc.
(The writer is President, Indian Medical Association, Manipur State Branch, and this article has been written following guidelines from MOHFW, GOI, ICMR, WHO, CDC etc. for public awareness).