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
- The new strains will keep on evolving as it’s a natural event and
practically impossible to change this factor of mutation etc.
- We can do a lot at the host factors and lots of guidelines are issued
by national/international organisations particularly WHO. The
importance of vaccination should be considered globally as well as
equity in vaccination etc. At the same time the efficacy of vaccines
on all different strains is yet unknown.
- At the environmental level also we can keep our environment safe by
adapting WASH and other guidelines to make world a safer place for
everyone.
- At last but not least global coordination is required to stop this
pandemic and any future mutations increasing virulence of covid-19
will have a detrimental effect globally if not stopped now through
international collaborations.
DECLARATION: This paper has not been previously published and
is not currently under consideration by another journal.