What the medical profession is seeing today has not been witnessed in over a century. A viral infection that is extremely difficult to treat spread rapidly and has now become a pandemic. It emerged from China a few months ago to cripple the whole world today. The last time such an endemic occurred was in 1918 when the Spanish Flu killed over 25 million people. Viruses: Viruses cause a variety of infection from a simple cold to the deadly Ebola infection. Most of the serious diseases caused by them have now been conquered through suitable vaccines. However every now and again a new form evolves. Most of these are tackled effectively by the body’s own immune system. Unfortunately a deadly form evolves from time to time when the body’s immune system is unable to fight it. The new Corona Virus that causes “Covid 19” infection is one such. It is a respiratory virus. How is the “New Corona Virus” different We have known about Corona Viruses for more than 50 years. So why are we panicking about this new virus. By exposure to many types of corona viruses in the past, our body’s defence mechanism has acquired suitable antibodies to fight an invading virus that is similar to the ones that it has encountered before. The New Corona Virus on the other hand is completely different to the ones that the body has been exposed to before. Therefore it does not have a ready antibody to fight the newcomer. The immune system has to generate a new antibody to fight the virus and that may take a few days. In addition to that the binding capacity (fusion) of the new corona virus to human cells appears to be more than 100 times stronger than those of any previously known corona viruses. Effect of the virus when it enters the human body: The virus is so named because it’s surface is covered by bulbous projections that look like a crown when viewed by an electron microscope. It is 0.125 micron in diameter (human hair is 100 microns). The surface projections are made up of protein that contains the infective material (the virion). When an infective droplet is inhaled, the virus can reach any area from the throat to the lung parenchyma (the alveolus). For the virus to multiply and infect the individual it must first enter the living cell. The glycoprotein spikes on the virus fuse to a suitable host cell and inject the infective material in to the cell. An enzyme called ACE2 which is present on certain cell membranes like the lungs, arteries, kidneys and intestines facilitates the spikes to fuse with the cell. Once inside the host cell they start replicating. The genetic material of the virus then makes the cell produce several copies of the virus. The new copy can then enter an adjacent cell and repeat the process. Thus within a short time the virus starts spreading. Symptoms of someone infected with the virus may vary from dry cough, fever or difficulty in breathing. Some may even complain of loss of taste or smell. If the individual is young and healthy it may cause only mild symptoms affecting the upper respiratory tract giving rise to fever or bouts of coughing. However if they have other co-existing conditions like high blood pressure, diabetes, chronic respiratory disease, obesity or if their immunity is compromised as when receiving treatment for cancer etc. the person may develop a more serious form of the disease affecting the lung. Older generation are also prone to develop a more serious form of the disease. When the lungs are affected, the lining membrane of the alveoli becomes inflammed giving rise to pneumonia. This results in the alveoli becoming filled with fluid and inflammatory cells. This affects the exchange of gases in the lung causing reduced amount of oxygen being carried in the blood. When the disease progresses further, more of the lung is affected. When the oxygen level in the blood drops below a critical level all the major organs can start to fail leading to death. Diagnostic tests for COVID 19: (fall into two broad categories) 1 . Swab Test: Molecular tests or Nucleic acid test of secretions from the nose and throat will detect the virus’ genetic code. 2 . Blood Test: Immunoassay will detect proteins (antigens or antibodies) associated with the virus. Nucleic acid-based tests are the most sensitive for early detection of infection. The test is called real time reverse transcription–polymerase chain reaction ( real time RT-PCR ). It is one of the most accurate laboratory methods for detecting, tracking, and studying the corona virus. A swab from an individual will collect mucous, saliva, bits of cells and with it viral RNA if it is present. The sample is then processed in the lab. Results are usually available within a few hours. Newer machines that can give you the result in under an hour are being developed and will soon be available on the market. Immunoassay: Usually blood, plasma, or serum is used for the test. Immunoassay detects the presence of specific immune proteins. The tests check for antigen or antibody in the specimen. Antigens are from the virus and antibodies are from the patients immune system. The tests use both virus specific antigen or antibody for the immunoassay. During the early stage of infection the viral antigens circulating in the blood will react with the antibody used in the test to indicate that the patient is infected. This is the basis for many of the “Rapid Antibody Tests”. A few days after an infection the patient is likely to produce antibodies. These antibodies will react with viral specific antigen to indicate the presence of ongoing or past viral infection. At the moment Immunoassay aren’t as sensitive as nucleic acid tests to detect infection during the early stages. However they are easier to use and would indicate that the individual became infected or was exposed to the infection a few days (or weeks) before the test. The test will be very useful for surveillance rather than for diagnosis. Corona viruses are the common cause of colds and other upper respiratory infections everywhere. Novel Corona Virus (the new corona virus) is an altered form of the same virus that can cause a serious disease that could turn fatal. So how do we know that the cold or cough that you have developed is not the usual ordinary cold or cough. Unless you are tested you may not know. The general advice now is, start treating any cold or cough with simple medication. As a precaution isolate yourself from the rest of the family, as you may still be infected with mild symptoms. Most people have only mild illness and usually recover at home without medical care. As the incubation period for the virus can be up to 14 days, isolation should be for 14 days. However if you develop a high fever, have difficulty controlling your cough or have difficulty breathing, you must request urgent medical help. If you are over 70 or have other co-morbid conditions like hypertension, diabetes, asthma, obesity or chronic heart disease you have to be extra careful and call for medical advice if any of the above mentioned symptoms are getting worse.. Do not wait until you have difficulty breathing. Treatment: Most people who get infected will recover well at home. All that is necessary is to isolate yourself from other family members and treat the infection as you would for a flu or cold. As of now there is no specific drug that will cure the disease. Paracetamol (acetaminophen) (max 3000 milligrams) can be prescribed for the pain and fever that may accompany the disease. Hydroxychloroquine and chloroquine have been shown to inhibit the virus from entering the cell. It has also been reported that it would kill the virus within the cell. However it does not help everyone and also they have other side effects on the heart etc and therefore not suitable for everyone. Until the scientists come up with a definite drug to cure the disease the main management now is to make sure the patient is comfortable, well hydrated, on a good diet and well oxygenated. Antibiotics are necessary only when they develop secondary bacterial infection following pneumonia. Hospital Treatment: According to WHO 80% of patients who have tested positive recover without the need to go in to hospital. However for the remaining 20% when symptoms get worse and breathing becomes difficult, they should be shifted to the hospital. Difficulty to breathe often indicates that the pneumonia is getting worse and oxygen level in the blood is dropping. Treatment in the hospital will consist mainly of isolating the patient with intensive support and administration of oxygen when necessary through the best possible means. Suitable antibiotics will be given to counter secondary bacterial infection when needed. Take Home Points: Covid 19 is a very virulent virus that spreads easily At the moment there is no curative medicine available to treat the infection Several vaccines are now being offered for the infection Although the vaccine may not prevent an infection you are unlikely to suffer the disease Avoid infection by staying away from crowds even after vaccination Wear a mask to prevent spread when you are out and about Maintain a safe distance from others in a public place If infection is suspected in a member of family, keep them isolated for 2 weeks Wash your hands with soap and water regularly (prevents transmission of infection This Topic is discussed in greater detail in the “Forum” under 1. Covid 19 infection; 2. Corona Virus Part I; 3. Corona Virus Part II
Covid 19 Infection
K. Badrinath, FRCS