Hence from the above facts it’s clear that agent is having continuous variations one of the factors responsible for the ongoing covid-19 pandemic. These viruses have crown like appearance produced by club shaped projections that studs the viral envelope. The coronavirus group actually infects a wide variety of animals of different species. These are divided into three antigenic and genetic groups.
Methodology – The explanation will be given to title through analysis of several accredited findings. The cause of perpetuation of Covid -19 can be understood by the way of infections and other related factors. SARS (SARS – CoV) CORONAVIRUSES causing human infections falls in group 1 and 2. The human isolates were HCoV-229E and HCoV-OC43. SARS-CoV was earlier considered to be a novel group of viruses (novel coronavirus, n covid-19) but now they are placed in group 2 (SARS-CoV-2). The fully sequenced have shown minimal variations.
The main problem in understanding morphology and other important determinants to know more about this virus is that it’s difficult to cultivate it in vitro added with continuous variations. We can grow some strains in human tracheal organ cultures but quite difficult to grow in tissue culture. SARS-CoV is exceptional as it can be grown in African green monkey kidney (Vero –E6) cells facilitating to know more about this virus.
Generally human coronavirus infections present globally. Seroprevalence studies have demonstrated this fact. The seasonal trends shows that infection is more common in late fall, winter, and early spring times. If we look at the history SARS-2002/2003 – south china outbreak begin with 8096 recognised cases in 28 countries & added to this 90 % of cases occurred in china and hongkong. Now the world is moving very fast or we can say the host factors related spread have exaggerated the pandemic added with various climatic changes. That time the natural reservoir of SARS-CoV appeared to be horseshoe bat. The 2002-2003 outbreaks thought to be originated due to human contacts with infected domestic animals. The striking fact is that in 2002-2003 as well as 2019-2020-2021 most cases spread from human to human and there are multiple ways of spread particularly respiratory droplets. The 2002 outbreak ceased in 2003 but 2019 outbreak is going on and global fast movement is one of the most important factors. The super spreaders may remain symptomless while spreading the virus.
Result- Several factors are responsible for the continuation of the pandemic. The pathogenesis of the strains causing common cold e.g. HCoV-229E and HCoV-OC43 says that they infect ciliated epithelial cells in the nasopharynx via the aminopeptidase 1 receptor (group 1) or a sialic acid receptor. Viral replication leads to a cascade of events manifested externally as common cold symptoms similar to other virus group called rhinoviruses.
SARS-CoV infects the respiratory tract via ACE 2 receptors. The systemic illness is manifested more or less depending upon immune status as well as associated morbidity conditions. The systemic manifestations include variety of signs and symptoms and sometime it’s symptomless. The study of pulmonary pathology will reveal more findings in coming days. One key finding is that earlier 2002-2003 outbreaks have many similarities with ncovid-19. The disease is milder in children and ARDS is also found in ncovid-19 severe cases. Besides this symptoms of common cold etc are very much similar. The incubation period is 1-14 days range. In earlier cases 2002-2003 laboratory findings have shown in SARS lymphopenia present in approx 50 % cases resulting in decreased immunity. Mostly T cells CD4+ (helper t cells) were affected and also CD8+T cell as well as natural killer to some extent.
The detailed information about ncovid-19 is yet to be finalised as several strains have been found and the trends shows that these variations will keep going. The global market has several accredited vaccines duly recognised by WHO. The final analysis and results can be declared only after a large population of world get vaccinated and with the development of herd immunity the predictions can be clearer.
Conclusion – In the epidemiological triad we have agent/host/environment. For controlling this pandemic of covid-19 as per public health approach our mind should be clear that we have to have a keen and deep view of epidemiological triad. The epidemiological triad (concept of causation) consist of agent (causative factor), host (those who get infected from agent) and the surroundings (ecology, environment etc.).
The modification at one of the above factors will modify other factors positively or negatively. Now we have to keep in mind that
DECLARATION: This paper has not been previously published and is not currently under consideration by another journal.