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The below mentioned article provides a short note on Corona Viruses.
Introduction to Corona Viruses:
Corona viruses (Corona, meaning crown) are spherical (100-150 nm in diam.), pleomorphic, enveloped RNA viruses containing petal- or club-shaped peplomers (spikes) on the surface.
Pathogenesis of Corona Viruses:
They are widespread in nature and infect a wide range of hosts. They have a variable tissue tropism in man. They cause Severe Acute Respiratory Syndrome (SARS). Corona virus family contains 11 recognised species which are divided into five groups on the basis of antigenic structure of N and M peplomer protein. Corona viruses have tropism for respiratory and gastrointestinal tract epithelial cells.
Human Corona Virus 2(HCV):
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In man, they cause upper respiratory tract diseases like common cold, severe acute respiratory syndrome (SARS). This HCV is responsible for 10% cases of common cold. It causes more coryza and discharge than rhino virus. Acquired immunity is not absolute. Reinfection with the same type of HCV is common in children of 4-10 years of age group.
SARS was reported first in China, then Hong Kong, Singapore. In India, the first SARS case has come from the place of sea and sand (Goal; Prasheet Warclhe (32 year old Goa), engineer who had sailed to Hong Kong and Singapore on March 30, 2003. He remained at the port for four hours before returning to Mumbai (India) on April 1,2003.
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His blood, sputum was found positive for SARS by National Institute of Communicable Disease (NICD) New Delhi (India), admitted at Goa Medical College Hospital, treated in isolation ward, a second round of test confirmed that he was SARS positive based on sample drawn on April 18, 2003. Later, he was discharged after few days’ treatment.
This disease, which is fatal in more than five per cent of cases and has no known cure has now killed 203 people and infected 3,900 around the world after first surfacing in southern China.
The genetic code is the raw material needed to develop a diagnostic test for SARS. The genetic code was broken by scientists of Genome Science Centre, Canada, on April 12, 2003. One could use these broken portions of this viral genome to test patients for infection by corona virus.
Scientists in several countries reported that SARS is most likely caused by a virulent new corona virus the type of virus that causes Influenza.
The genetic sequence was broken by scientists on April 12, 2003. This new information will tell if SARS virus genome resembles other viral genome and give hints about the biology of this virus. A team of experts from World Health Organisation (WHO) has introduced in China a safe testing method based on the sequencing of the virus genome to test the virus within an hour.
This new method uses the specially modified protein of the virus to detect the presence of a type of antibody which the body produces as a response to infection with the virus. This is “quick new test for virus, corona virus”.
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Suspected SARS cases were reported from different parts of India (New Delhi, Nasik, Jaipur, Kerala, Kolkata, Pune, Mumbai). The total number of SARS cases in India had now gone up to seven confirmed.
Nine more SARS cases, mostly of health workers had been confirmed from Pune taking a total number of those WHO have tested positive to 19. In Amritsar (Punjab) a 85 year old man, who did not travel to any of the SARS affected countries, was tested positive for SARS in the initial tests.
The global toll from SARS climbed above 500 dead, 7,000 infected on Thursday (May 8, 2003 as the World Health Organisation (WHO) declared that the disease is far more deadly than it was previously thought.
Heinz Felfmann, head of WHO investigating team, confirmed SARS virus spreads by droplets and is not borne.
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By July 3, when the pandemic was controlled, it had affected over 30 countries, with many thousand cases & over 800 deaths. India escaped the epidemic. No further outbreak has occurred after that till 2011.
Laboratory Diagnosis of Corona Viruses:
1. Isolation of human corona virus in cell culture is difficult. Some strains have been grown in organ cultures of human embryonic trachea in research centre.
2. Direct demonstration of virus respiratory secretions can be made by ELISA test with high titre anti-serum.
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3. Serological test: CFT, ELISA and haemagglutination test become positive.
