OVERVIEW
OF
VIRAL INFECTIONS
Anurag Kumar Diksha Jha
Anushka Gupta Fahad Khan
Ashi Tripathi Fatima
Chaturvedi Bushra
Aastha Ganesh
Deepak Raj Dutta
Gauri
Middha
INTRODUCTION
Viruses are smallest (unicellular) obligate intracellular infective agent. It has no
 metabolic activity outside host cells.
Viruses comprises of:-
(i) Envelope
(ii) Protein coat (capsid)
Nuclei acid (DNA or RNA)
(iii)
ENVELOPE
It surrounds nucleocaspid
\ and is lipoprotein in nature.
Lipid part is from host cell and protein part is bacterial coded,
subunit called Peplomere.
This peplomere are antigenic and bind to specific receptors on host cell.
PROTEIN COAT - CAPSID
It is composed of number of repeated subunits called as Capsomere.
Functions of capsid:-
Protects the nuclei acid core.
In non enveloped virus, role in viral replication by attaching to specific receptor off host
cell
It is antigenic and specific for each virus.
Size
Nucleic acid classification of
viruses
\
Attachment → Penetration → Uncoating → Biosynthesis →
Assembly → Maturation → Release.
VIRAL REPLICATION
\
PATHOGENESIS
Most of the viral infections progress
through the
\
following steps inside the human body:-
Transmission (entry into the body)
Primary site replication
Spread to secondary site
Manifestations of the disease.
HERPES VIRUS
HERPES SIMPLEX VIRUS
Belongs to alpha sub family of Herpesviridae
Replication:- 12-18hrs
2 types:- HSV-1;HSV-2
\
PATHOGENESIS :-
HSV-1 oropharyngeal contact (above the waist)
HSV -2 sexual contact (below the waist)
CLINICAL MANIFESTATION :-
Oral facial mucosal lessons
Cutaneous lessons
Herpetic whitlow
Febrile blisters
EPIDEMIOLOGY :-
Varicella -zoster virus
HSV -1. Infected secretion ( saliva)
+ cytomegalovirus +
Epstein
HSV -2. Sexual or vertical routes Barr
CYTOPATHOLOGY :-
Ballooning of infected cell
Margination of chromatin
VARICELLA ZOSTER
\ VIRUS
1) Chickenpox
Generalised diffused bilateral vesicular rashes
Highly contagious
2) Zoster or shingles
Reactivation of latent VZV in adult life
Rashes (unilateral and segmental)
PARVOVIRUS
Simplest and Smallest (28-/26nm) animal
virus.
DNA Virus Single stranded DNA
Most common Parvovirus: B19
Transmission:-
transfusion, Respiratory rouge, Blood
Trans placental route
Clinical manifestation:-
\
Erythema Infectiosum
Transient apalstic crisis
PAPILLOMA VIRUS
•DNA Virus
•Belongs to Papillomaviridae family
Infections caused:
•Benign wart
•Common skin wart
•Plantar wart
•Anogenital wart
POX VIRUS
Largest virus (40×230 nm).
Brick shaped or ellipsoid.
Single linear
\ ds-DNA.
Pox virus of human importance
SMALLPOX
Variola: Causative Agent
First infectious disease
ADENOVIRUS
Double Stranded DNA virus
Non enveloped virus
Adenovirus infect and replicate in epithelial cells and
produce various infections for example infection of
respiratory tract (upper respiratory tract infections,
pneumonia) \
Associated in recombinamt vaccines
Human adenovirus vector Covishield chimpanzee
adenovirus
BACTERIOPHAGE
Bacteriophages are the virus that infect
bacteria.
Bacteriophage - Life cycle
Significance /Uses of
bacteriophage
Phage typing
\ Used in treatment
Used as cloning vector
Transfer drug
resistance
Code for toxins
MYXOVIR
Myxoviruses are a group of virusesUS
that
bind to mucin receptors on the surface of
RBCs (myxo in Greek meaning 'mucin');
resulting in clumping of RBCs together to
cause hemagglutination.
\
Myxoviruses are divided into two families:-
(1) Orthomyxoviridae
(2) Paramyxoviridae
Both differ from each other in various
aspects; the most important difference is
the presence of segmented RNA in
Orthomyxoviridae family.
ORTHOMYXOVIRIDAE
Influenza viruses are the members of
Orthomyxoviridae\ family. They are one of
the major causes of morbidity and
mortality and have been responsible for
several epidemics and pandemics of
respiratory diseases in the last two
centuries.
PARAMYXOVIRUS
Paramyxoviridae contains of a group of viruses, which
are transmitted via the respiratory route following
which:
• They may cause localized respiratory infection in
children ( e.g. respiratory
\ syncytial virus and the
parainfluenza viruses)
• They may disseminate throughout the body to cause
highly contagious diseases of childhood such as mumps
virus (parotid enlargement) and measles virus (rashes).
• It also includes viruses such as Newcastle Disease
virus (cause self limited conjuctivitis in poultry workers),
Nipah and Hedra viruses.
RUBELLA VIRUS
It is in paramyxoviridae but belongs to togaviridae arbovirus.
It is highly teratogenic and causes congenital malformation
affecting organs such as eyes ear and heart in fetus.
Infectivity period _rash \1 week before and 1 week after
Incubation period 2-3 weeks
Congenital rubella syndrome had it classical triad
Cataract
Heart disease
Deafness
Live attenuated vaccine is available for rubella ;
recommended for children and young women.
CORONAVIRUS
Coronaviruses (CoV) cause Respiratory tract infections in humans.
Coronaviruses causing human infections mostly belong to the
Betacoronavirus.
SEVERE DISEASES :-
SARS-CoV (Severe acute respiratory syndrome)
MERS-CoV (Middle east respiratory syndrome)
SARS-CoV-2 (Severe acute respiratory syndrome coronavirus-2)
MORPHOLOGY :-
They are linear, enveloped ssRNA.
Club shaped or Crown like peplomer spikes giving appearance of a Solar Corona.
They are spherical large (12-160 nm) viruses having Helical symmetry.
COVID-19
COVID-19 is a acute respiratory disease caused by SARS-CoV-2.
This virus caused a pandemic which originated in Wuhan, China in December 2019 and
subsequently spread to the world over 3-4 months.
Over 67 crore cases with >67 lakh deaths were reported as of
January 2023, with overall mortality rate of 1%.
India experienced 3 different COVID waves and accounts for
Second highest number of cases.
SARS-CoV-2 VARIANTS :-
Alpha, Beta, Gamma, Delta (2 wave), Omicron (3 wave).
nd rd
MORPHOLOGY :-
RNA virus comprises of nucleocapsid with Helical symmetry
surrounded by an envelope.
4 Structural Proteins:
Nucleocapsid protein, Spike protein, Membrane glycoprotein, Envelope protein.
CLINICAL MANIFESTATIONS :-
Incubation Period: 5-6 days but can be long as 14 days.
Symptomatic patients :-
MILD: ILI (Influenza like illness)
MODERATE: Pneumonia
SEVERE: Severe Pneumonia with Complications like Acute respiratory distress syndrome, Sepsis,
Septic shock, etc.
TRANSMISSION :-
# Respiratory droplets # Contact routes # Aerosol transmission
PREVENTION & CONTROL:-
# Hand hygiene # Social distancing # Sanitization # Masks # PPE # Quarantine
VACCINES :-
# Covishield # Covaxin # Sputnik V vaccine
LAB DIAGNOSIS :-
Real time RT-PCR
Antigen Detection Assay
Antibody (IgG) detection assay
PICORNAVIRU
S
POLIOVIRUS
Poliovirus, the causative agent of poliomyelitis.
PATHOGENESIS: transmitted by faeco-oral route Spreads to
CNS/spinal cord by hematogenous route.
CLINICAL MANIFESTATIONS: rarely progresses to aseptic
meningitis.
And paralytic polimyelitis.
VACCINE: killed injectable and live oral polio vaccine.
ERADICATION: it is now at the verge of eradication as extensive
immunization program are being conducted globally.
COXSACKIEVIR
US
It is a type of Enterovirus
Produces a variety of clinical illnesses in human:
Meningitis
Conjunctivitis
Myocarditis
Pericarditis
Pancreatitis
ARBOVIRUS
Arbovirus(arthropod-borne viruses) diverse group of RNA viruses
PATHOGENESIS: Transmitted by blood sucking arthropods
CLINICAL MANIFESTATION: hemorrhagic fever and encephalitis
Some of the arbovirus which are prevalent in India are;
DENGUE VIRUS
VECTOR: Aedes aegypti & Aedes albopictus
CLINICAL MANIFESTATION: present in three stages
-Dengue fever
-DENGUE hemorrhagic fever
-Dengue shock syndrome
DIAGNOSTIC TEST: ELISA and reverse transcripts PCR
CHIKUNGUNYA VIRUS
VECTOR: Aedes aegypti mosquito
CLINICAL MANIFESTATION: fever, arthritis, rarely hemorrhagic fever
JAPANESE B ENCEPHALITIS
VECTOR: Culex tritaeniorhynchus
RABIES
It causes Acute infectious disease of the CNS in humans & animals
TRANSMISSION: another infected animal bite( most commonly dog)
CLINICAL MANIFESTATION: - spread from Site of bite CNS
- Produces acute neurologic phase which
maybe an encephalitic or paralytic type.
-Encephalitic type causes hyperexcitability,
hydrophobia.
-Gradually develops coma & leads to death
LAB DIAGNOSIS: detection of rabies by. •Direct IF test •RT PCR
HIV
Human Immunodeficiency Virus (HIV) is the causal agent of Acquired Immunodeficiency
Syndrome (AIDS).
STRUCTURE :-
They are spherical, ranging from 80-110 nm in size.
ENVELOPE: Lipid part, Protein part (gp120 & gp41)
NUCLEOCAPSID: Capsid has Icosahedral symmetry; made up of core protein.
RNA- ssRNA linear RNA
ENZYMES- Reverse transcriptase, Integrase, Proteases.
MODE OF TRANSMISSION:-
Sexual Mode – Most common; 75% of total cases
Blood Transfusion – Least common; 90-95% of cases
Percutaneous/Mucosal – Less transmission; about 10% of cases
Perinatal Mode – 20-40% transmission; 10% of cases
VIRAL
Fusion
REPLICATION
Penetration & Uncoating
Reverse transcription
Pre-Integration complex
Integration
Latency
LAB DIAGNOSIS :-
Specific Tests (1) Screening Tests – Antibody detection
ELISA (2-3 hrs)
Rapid/Simple test (<30 min)
(2) Supplement Tests – Antibody detection
Western blot assay
Line immunoassay (LIA)
(3) Confirmatory Tests
P24 antigen detection
Viral culture – by Co-cultivation technique
HIV RNA (Best confirmatory method)
HIV DNA detection
Non-Specific (1) Low CD4 T cell count
(2) Hypergammaglobulinemia
(3) Altered CD4:CD8 T cell ratio
HEPATITIS
Hepatitis viruses are heterogeneous group of viruses.
These are hepatotropic and produce similar clinical
illness such as fever,nausea,vomiting and jaundice.
Hepatitis A to E are RNA viruses except HBV which
\
is a DNA virus.
Hepatitis A and E:
-transmitted by fecooral route
-do not have carrier stage or chronicity
Hepatitis B,C and D:
-transmitted by percutaneous,sexual or vertical routes
-disease may progress to carrier stage, chronic hepatitis or
Hepatitis
LABORATORY DIAGNOSIS
Includes detection of various viral markers
such as:
-Detection of viral antigens ( eg-HBsAg for
HBV)
-Detection of antibodies
\ (eg-anti-HCV and
anti-HEV)
-Detection of viral nucleic acid (By PCR)
TREATMENT
Antiviral drugs are available such as:
-Tenofovir and telbivudine for HBV
-Interferon,ribavirin for HCV
Vaccines are also available for HAV and HBV.
MISCELLANEOUS VIRUS
Rodent-borne viruses
~transmitted from rodents to man by contact
with infected
\
body fluids or excretions. Major viruses include:
-Hantaviruses: causes hemorrhagic fever with
renal syndrome and hantavirus pulmonary
syndrome.
-Arenaviruses: cause various diseases such as
South American hemorrhagic fever
Filoviruses
~ Includes Ebola virus and Marburg virus.
~ Cause hemorrhagic fever
~ Transmission by\ close contact with
blood or other body fluids.
Viral gastro entritis
~ Eg- rotavirus, adenovirus,
calicivirus and astrovirus.
~ Most commonly affects children.
Slow viruses and prions
Slow viruses and prions
~These are a group of neurodegenerative conditions
affecting both humans and animals.
~These are characterised
\ by: long incubation period,
Predilection for CNS ans a strong genetic predisposition.
~conventional slow viruses:
Eg- subacute sclerosing panencephalitis
~unconventional viruses:
Eg- prion disease
LABORATORY DIAGNOSIS OF VIRAL DISEASES
1. Direct Demonstration of Virus
Viral gastro entritis
• Electron microscopy
• Immunoelectron microscopy
• Fluorescent microscopy
• Light microscopy:
-bodies
Histopathological staining: To demonstrate inclusion
- Immunoperoxidase staining.
2. Detection of Viral\ Antigens
By various formats such as ELISA, direct IF, ICT, flow
through assays.
3. Detection of Specific Antibodies
• Conventional techniques such as HAI, neutralization test
and CET
• Newer diagnostic formats such as ELISA, ICT, flow
through assays.
4. Molecular Methods to Detect Viral Genes
• Nucleic acid probe--for detection of DNA or RNA by
TREATMENT OF VIRAL DISEASES
Interferons
Viral Vaccines:\ Killed Viral Vaccine , Subunit Vaccines, Live
vaccine
Passive Immunization
Combined Immunization
BIBLIOGRAPHY
Apurba S Sastri
C. P. Baveja
Ananthanarayanan and Paniker
www.diginerve.com
