cover19

Corona virus is a large family of viruses that are found in both animals such as camels, cats, bats, etc. and in human beings. There are about seven different strains of corona virus.

1. 229E (alpha coronavirus)

2. NL63 (alpha coronavirus)

3. OC43 (beta coronavirus)

4. HKU1 (beta coronavirus)

5. Middle East Respiratory Syndrome, abbreviated as MERS-CoV of beta coronavirus

6. Severe Acute Respiratory Syndrome, abbreviated as SARS-CoV of beta coronavirus

7. Severe Acute Respiratory Syndrome – Novel Coronavirus, abbreviated as SARS-CoV-2 or Covid – 19

Sometimes corona virus from animals can infect people and spread further via human to human transmission such as with MERS-CoV, SARS-CoV, and now with this COVID-19. The virus causing COVID-19 is designated as severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) previously, now referred as 2019-nCoV. In December 2019, novel corona virus was identified as a cause of upper and lower respiratory tract infections in Wuhan, a city in the Hubei of China. Its rapid spread, resulted in an epidemic throughout China and then gradually spreading to other parts of the world leading to the pandemic. With exclusion of Antartica, almost every continent has been affected.

Understanding the mode of transmission is currently incomplete. Epidemiologic investigation in Wuhan at the beginning of the outbreak had an initial association with a seafood market where most patients had worked or visited. It was considered that the virus originated from snakes, however later studies proved that it also had more similarity with bats. As the Covid 19 outbreak progressed, person-toperson transmission through droplets and fomites became the primary mode of transmission.

Droplet transmission

When a person who is an infected one can cause its spread if he coughs, sneezes brings the virus makes its way and releases itself into the secretions of respiratory tract. These droplets infect others if they make direct contact with the mucous membranes. Infection may spread by touching an infected surface and followed by eyes, nose or mouth. Droplets typically do not travel more than six feet and do not sustain in the air. Airborne precautions are recommended routinely in some countries and also in the setting of specific high risk procedures. Spread of infection is also possible before symptoms appear.

Other possible modes of transmission

A person can get COVID-19 by touching a surface or object that has the virus on it and touching their own mouth, nose, or their eyes, but this very unlikely way the virus spreads. RNA particles of Covid – 19 has also been detected in biological samples such as urine and feces of few patients. There are evidences of SARS-CoV-2 viable in the urine of few patient. Studies have also cultured SARS-CoV-2 from stool specimens. But, there has been no published reports of transmission of SARS-CoV-2 through feces or urine.

It is reported that SARS-CoV-2 RNA, has been detected in plasma and serum, the virus can replicate in blood cells. At present, there is very less evidence to prove intrauterine transmission of Covid – 19 virus from infected pregnant women to their fetuses. WHO recommended that suspected or infected mothers should continue to breastfeed. In February, a Chinese mother was tested positive before parturition and her newborn was diagnosed with the new coronavirus within 30 hours after birth. The route of transmission could not be ascertained, whether it was intrauterine or after delivery. Observing the evolution of the COVID-19 epidemic in China, it was noticed that there was substantial heterogeneity in the size of the epidemic of cities across the country. Thus, the studies were done to identify some essential questions to the transmission of COVID-19 raised by the reality with the evidences from China. Firstly, some cities have more infected cases, while some other cities have less. Secondly, to understand the role of the distances of these cities with confirmed cases to the epicenter of the outbreak of an infectious disease with large scale. Third, was to identify the lessons of the transmission from the urban characteristics of those cities which are infected. Fourth, important objective was to know if there is a quantitative model which can predict the actual infection scale of the epicenter precisely with the information of the epidemic in other cities. People need to pay more attention to the social and urban fundamentals of the transmission of COVID-19, not only the biological features of the virus. In a particular perspective, the current ongoing epidemic of COVID-19 can be treated as an urban incident as well, which has caused substantial challenges to the urban management or even urban planning. Therefore, dealing with the current epidemic using urban regulatory methods, needs attention on how to prevent it from ever happening in the future. Due to the technical obstacles and high cost for the laboratory-confirmation of COVID-19, it is uncertain to know the exact scale of the infection at the epicenter of the outbreak in its early or even middle stage. Especially in the initial stage of the epidemic in the epicenter, there can be substantial unknown infection numbers. Thus, precise estimation of the real infection scale is badly needed. Similarly it is important to understand the scale of the epidemic with other emerging regions at high risk of epidemic, before it is too late to contain the epidemic situation. The correct estimates of the size of the epidemic are crucial to prepare and allocate appropriate medical resources to save lives.

As the coronavirus disease pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS Cov-2) unfolds, a bigger number of incidences have indicated that not all infected persons exhibit signs or symptoms of ill¬ness, including persons who are presymptomatic. RNA of Covid-19 virus is detectable before onset of symptom or in asymptomatic stage. SARS-CoV-2 RNA is de¬tectable but symptoms never develop. The de¬tection of SARS-CoV-2 RNA in presymptomatic and asymptomatic persons does not necessarily make them the medium of transmission to others. When an infected person can spread SARSCoV-2 it is important to know as how the virus spreads. Thus, maximum viral loads of SARS-CoV-2 RNA can be detected in asymptomatic people 1-3 days before their symptoms appear and it can be measured by RT-PCR. It is observed that there is high viral load around the day of symptom onset, followed by a gradual decline over time. The duration of getting positive finding with RT-PCR was approximately 1-2 weeks in patients who are having no symptoms, 3 weeks or more in patients who are having mild to moderate disease and it was even more in patients with severe disease. It is clear from available evidence, that limiting close contact between infected people and others is of central importance in breaking chains of transmission of the virus causing COVID-19. To prevent transmission, it is important to identify the suspected cases as soon as possible followed by testing and then isolating infectious cases. It is equally important to identify all close contacts of infected people and quarantine them to prevent spread and break chains of transmission. The incubation period of COVID-19 is on an average of 5-6 days, but can be as long as 14 days. Therefore, quarantine should be in for 14 days from the last exposure to a confirmed case. DIAGNOSIS OF COVID -19 Rapid antigen detection test for detection of Covid-19 – In this test we detect antigens that are found on or within Covid-19 virus. This test can be performed outside the routine laboratory set up also, even in field work and is a very quick test. The kit includes a sterile swab (Sample collection Swab), an inbuilt test device, viral extraction tube and viral lysis buffer. Currently, the gold standard test is RT-PCR. In the same hypothesis, rapid antigen detection test also detects the virus particles and not the body’s immune responded antibody. Time is the main difference between these two tests. The rapid antigen test gives a qualitative result in maximum 30 minutes, while RT-PCR takes about minimum 5 hours and also needs time for sample transportation as RT-PCR requires a conventional laboratory set up. In containment zones, the rapid test can be conducted on all symptomatic influenza-like illnesses. False positive rates from Rapid antigen test are very less while false negatives are bit high. i.e. Sensitivity of rapid antigen test is less but Specificity is high. Considering this point, negative result by rapid antigen test should be confirmed by RT-PCR for making treatment policy or to prevent spread of infection in community

As the coronavirus disease pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS Cov-2) unfolds, a bigger number of incidences have indicated that not all infected persons exhibit signs or symptoms of ill¬ness, including persons who are presymptomatic. RNA of Covid-19 virus is detectable before onset of symptom or in asymptomatic stage. SARS-CoV-2 RNA is de¬tectable but symptoms never develop. The de¬tection of SARS-CoV-2 RNA in presymptomatic and asymptomatic persons does not necessarily make them the medium of transmission to others. When an infected person can spread SARSCoV-2 it is important to know as how the virus spreads. Thus, maximum viral loads of SARS-CoV-2 RNA can be detected in asymptomatic people 1-3 days before their symptoms appear and it can be measured by RT-PCR. It is observed that there is high viral load around the day of symptom onset, followed by a gradual decline over time. The duration of getting positive finding with RT-PCR was approximately 1-2 weeks in patients who are having no symptoms, 3 weeks or more in patients who are having mild to moderate disease and it was even more in patients with severe disease. It is clear from available evidence, that limiting close contact between infected people and others is of central importance in breaking chains of transmission of the virus causing COVID-19. To prevent transmission, it is important to identify the suspected cases as soon as possible followed by testing and then isolating infectious cases. It is equally important to identify all close contacts of infected people and quarantine them to prevent spread and break chains of transmission. The incubation period of COVID-19 is on an average of 5-6 days, but can be as long as 14 days. Therefore, quarantine should be in for 14 days from the last exposure to a confirmed case.

DIAGNOSIS OF COVID -19

Rapid antigen detection test for detection of Covid-19 – In this test we detect antigens that are found on or within Covid-19 virus. This test can be performed outside the routine laboratory set up also, even in field work and is a very quick test. The kit includes a sterile swab (Sample collection Swab), an inbuilt test device, viral extraction tube and viral lysis buffer. Currently, the gold standard test is RT-PCR. In the same hypothesis, rapid antigen detection test also detects the virus particles and not the body’s immune responded antibody. Time is the main difference between these two tests. The rapid antigen test gives a qualitative result in maximum 30 minutes, while RT-PCR takes about minimum 5 hours and also needs time for sample transportation as RT-PCR requires a conventional laboratory set up. In containment zones, the rapid test can be conducted on all symptomatic influenza-like illnesses. False positive rates from Rapid antigen test are very less while false negatives are bit high. i.e. Sensitivity of rapid antigen test is less but Specificity is high. Considering this point, negative result by rapid antigen test should be confirmed by RT-PCR for making treatment policy or to prevent spread of infection in community.

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Amit Agrawat

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– Dr. Amit Agravat

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