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1. GONO BISHWABIDYALAY
Nolam,Mirzanagar,savar,Dhaka-1344
DEPARTMENT OF MICROBIOLOGY
An Assignment On : Pathogenesis Of COVID-19
Course Title : Immunology-I
Course code : 3601
Submitted To Submitted By
Mumtarin Jannat Oishee Name : (Group-2 Md Shamim Hossain, Robel mia,
Sangeeta Mazumder , solaiman)
Assistsnt Lecturer Exam Roll :( 1222,1221,1217. 1216)
Department Of Microbiology Batch No : 33rd
Gono Bishwabidyalay Semester : 6th
Submission Date : 09-01-2021

2. Introduction
Coronaviruses are enveloped non-segmented positive sense RNA viruses belonging to the family
Coronaviridae and the order Nidovirales and broadly distributed in humans and other mammals. Size 100-
160nm , Although most human coronavirus infections are mild, the epidemics of the three
betacoronaviruses, severe acute respiratory syndrome coronavirus (SARS-CoV) , Middle East respiratory
syndrome coronavirus (MERS-CoV) and Novel coronavirus or (SARS-CoV-2).
The coronavirus (severe acute respiratory syndrome coronavirus 2 of the genus Betacoronavirus ) that is
the caugetive agent of COVID-19 .
Structure
Coronaviruses contain a canonical set of four major structural proteins: the spike (S), membrane (M), and
envelope (E) proteins, all of which are located in the membrane envelope, and the nucleocapsid (N) protein,
which is found in the ribonucleoprotein core .
Types of corona Virus
There are now 7 types of coronaviruses that have been identified by the CDC , which includes
Common human coronaviruses
1. 229E (Alpha coronavirus)
2. NL63 (Alpha coronavirus)
3. OC43 (Beta coronavirus)
4. HKU1 (Beta coronavirus)
Other human coronaviruses
5. MERS-CoV (Beta coronavirus that causes Middle East Respiratory syndrome, or MERS )
6. SARS-CoV (the Beta coronavirus that causes a severe acute respiratory syndrome,or SARS)
7. Novel coronavirus (SARS-CoV-2)
Pathogenesis
After the virus enters the body, it needs a special receptor to help it enter the cell. This receptor is called
(Angiotensin Converting Enzymes - 2) Symbolized by ACE-2. The ACE-2 is present on the surface of the
alveolar cells in the lung.
We have 3 types of alveolar cells:
1. Responsible for gas exchange.
2. It is responsible for producing "surfactant" which is a mixture of proteins and fats that reduce the surface
tension of the alveoli.

3. 3. Dust cell, which is macrophages.
The ACE_2 is found on type 2 of these cells. Corona virus envelope contains proteins called spikes and
special (S-Spike) that help the virus bind to ACE-2.
When the above association occurs, the genetic material of the virus enters the cell and the cell is harnessed
to produce viral proteins, thus the virus multiplies and the cell dies.
When (type 2 alveolar cells) die, they release substances called specific inflammatory mediators .
These substances stimulate the existing immune cells "macrophages" and when they stimulate the
macrophages.
they secretes 3 immune substances called "cytokines" which are:
1. Interleukin - 1 (IL-1)
2. Interleukin - 6 (IL-6)
3. Tumor Necrosis Factor (TNF-α).
These three substances, when they reach the blood stream, cause the symptoms associated with infection
with Corona virus.
SYMPTOMS
The primary symptoms of SARS CoV-2 include :
1. Cough
2. Fever
3. Shortness of breath
4.Fatigue
Less common symptoms of SARS CoV-2 include:
1. Sore throat
2. Nasal congestion
3. Aches and pains
4. Diarrhea
Symptoms

4. First - at the level of lungs:
These substances cause expansion of the blood vessels surrounding the vesicle, as well as increased
permeability of the wall of these vessels
> Vasodilation
> Capillary permeability increased. and thus leads to "alveolar edema", which leads to hypoxia and
shortness of breath.
The loss of surfactant leads to an increase in the surface tension of the vesicle and consequently leads to
Alveolar collapse. It also leads to Hypoxia and shortness of breath.
These three substances also lead to an increase in the flow of "neutrophils" cells to the place of the viral
infection as an immune response. Neutrophils cells kill some viruses by secreting two substances such as:
1.Reactive Oxygen Species "ROS’’
2.Proteases.
But the above articles also destroy some of the alveolar cells responsible for gaseous exchange and cause a
condition called consolidation that causes cough symptoms.
Second: At the CNS level:
The three substances "IL-1, IL-6, TNF" go to the "hypothalamus" and thus increase the body temperature
and cause the symptoms of "Fever".
Third:
In the case of severe "SIRS" will occur Systemic inflammatory response syndrome. That lead to septic
shock. Also "MODS" Multiple organ dysfunction syndrome. Especially the kidney and kidney failure.
Host Range
Natural hosts include humans, Himalayan palm civets (Paguma larvata), racoon dogs (Nyctereutes
procyonoides), Chinese ferret badgers (Melogale moschata), cats, and pigs. Experimental hosts include non-
human primates, ferrets, golden hamsters, guinea pigs, mice, and rats.
Mode of Transmission
Person-to-person contact (direct mucous membrane contact (eyes, nose and mouth) with infectious
respiratory droplets and/or direct contact with infected body fluids) and/or through exposure to fomites.
Other possible modes of transmission include through blood transfusions, or by sharps injuries.
Incubation Period
The incubation period of SARS CoV-2 ranges from 2 to 14 day
Reservoir
Bats are thought to be the natural reservoir for SARS-CoV-2. Research is ongoing to identify the specific
reservoir species. SARS-CoV-2 like viruses with a high degree of sequence homology with SARS-CoV-2
were found in horseshoe bats (Rhinolophus spp.). On the other hand, the horseshoe bat angiotensin-

5. converting enzyme 2 (ACE2) was found in one study to be unable to act as a receptor for human SARS-
CoV-2, unlike its human equivalen. Rhinolophus sinicus (Chinese Rufous Horshoe Bat) and Myotis
daubentoni (Daubenton’s Bat) were found to be susceptible to SARS-CoV-2 infection in this same study.
Prophylaxis or prevention
The following Basic protective measures can help you protect yourself from SARS CoV-2
1. Stay Home : According to the centre for disease control the best way to protect yourself from the virus is
to avoid being exposed to it. That means staying home to avoid coming into contact with people who might
have the virus.
2. Wash your hands often and thoroughly: Wash your hands with soap and water for at least 20 seconds
especially if you have been in a public area.
3. Use an alcohol – based hand sanitizer .When its not possible to wash your hands, use a hand sanitizer
with at least 60% alcohol content.
4. Avoid touching your face : The virus can servive on surfaces that you touch with your hands . If your
hands come into contact with your mouth, nose, and eyes, the virus might enter your body.
5. Practice social distancing : If you need to leave your house, maintain your distance from anyone who
might have the virus, especially if the virus is being transmitted in your community. The centre for disease
control recommends staying at least 6 feet (1.83 meters) away from others.
6. Seek regular updates : The situation is evolving rapidly.It’s important to follow instructions from public
health officials