1. بسم الله الرحمن الرحيم VIRAL INFECTION By: Dr.Malak El-Hazmi
Assistant Professor & Consultant Virologist College of Medicine & KKUH

2. Objectives ; At the end of this lecture , the student is expected
to know;
1- the general characteristic of viruses and differentiate them from other living organisms .
2- how viruses are transmitted , how can produce diseases & types of viral infections ( pathogenesis ) .
3- some example of viral diseases (skin rash , hepatitis
& AIDS)
4- general information on treatment & prevention .

3. Lecture contents Introduction to viruses; Viral Pathogenesis;
Characteristics of viruses
Viral Structure
Symmetry
Viral Pathogenesis;
Route of transmission
Mechanisms of spread of virus through the body
Important features of Acute Viral Diseases
Types of viral infections
Examples of viral diseases
Treatment
Control and prevention

4. Properties of Microorganisms
characteristic
Parasite
Fungi
Bacteria
Virus
Cell
Yes No
Type of
nucleus
Eukaryotic
Prokaryotic
-----
Nucleic acid
Both
DNA
& RNA
Both DNA
Both DNA
DNA or RNA
Ribosome
Present
Absent
Mitochondria
Replication
Mitosis
Budding or
mitosis
Binary fission
special

5. Characteristics of viruses
Viruses are not cells.
They lack cellular organelles ,
such as mitochondria & ribosome .
They are obligate intracellular parasites .
They multiply only within cells ,
because they cannot generate energy or synthesize protein
They replicate in a manner different from cells.
One virus can replicate to produce hundreds of progeny viruses

6. Viruses are smaller than bacteria
Viruses are smaller than bacteria. They range in size between 20nm (poliovirus)- 300nm(small poxvirus)

7. Viral Structure Viruses are composed of
nucleic acid either DNA or RNA , surrounded by a protein coat called the capsid.
The capsid is composed of small structural units called capsomeres.
Some viruses have lipoprotein envelope

8. Symmetry based on arrangement of capsomeres
1-Cubic symmetry ( Icosahedral )
Capsomeres are arranged in 20 triangles to form an icosahedron
The virus particle is spherical
Adenovirus Herpesvirus

9. Symmetry based on arrangement of capsomeres
2- Helical symmetry
Capsomeres are arranged round the spiral nucleic acid
The virus particle is either
Elongated
(filoviruses)
Pleomorphic
( influenza v.)
3- Complex symmetry
The virus particle does not conform either cubic or helical symmetry e.g. Small pox virus

10. Match Cells Viruses are RNA Capsid Viruses lack Particles
Symmetry
Envelope
mitochondria
Viruses are
Viruses lack
Viruses have 3 forms of
Viruses must replicate in
Some viruses have

11. Answers Viruses are Particles Viruses lack Mitochondria
Viruses have 3 forms of Symmetry
Viruses must replicate in Cells
Some viruses have Envelope

12. Pathogenesis Transmission of the virus & its entry into the host.
Replication of the virus & damage to cells
Viruses remain localized or spread to other organs
The immune response as
Host defense & a contributing cause of certain disease
5. Persistence of virus in some instance

13. Transmission Person to person Animal to person Horizontal transmission
Skin contact ,Blood
Respiratory route
Fecal - oral route
Genital contact
Vertical transmission
Animal to person

14. Common Routes of Human Infection by Viruses
Route of Entry
Virus
Disease (Localized /Systemic)
Skin
Mild Trauma
HPV
Warts (L)
Injection (Blood)
HBV,HCV, HIV
Hepatitis B, Hepatitis C ,AIDS (S)
Bite of insect
animal
Yellow fever virus
Rabies virus
Yellow fever (S)
Rabies (S)
Respiratory tract
HSV-1
Rhinovirus
RSV
Adenovirus
VZV
Measles virus
Gingivostomatitis (L) (URT)
Common cold (L) (URT)
Bronchiolitis (L) (LRT)
Pneumonia (L) (LRT)
Chickenpox (S)
Measles (S)
GIT
Rotavirus
HAV
Poliovirus
Diarrhea (L)
Hepatitis A (S)
Poliomyelitis (S)
Genital tract
HSV-2
HBV
HIV
Genital herpes (L)
Meningitis (S)
Encephalitis (S)
Hepatitis B (S)
AIDS(S)

15. Mechanisms of spread of virus through the body

16. Important features of Acute Viral Diseases
Local Infections ( L )
Systemic Infections ( S )
Ex. of specific Disease
Rhinovirus
Measles
Site of Pathology
Portal of entry
Distant site IP
Relatively short
Relatively long
Viremia
Absent
Present
Duration of Immunity
Variable- may be short
Usually life long
Role of Secretory AB [IgA]
in resistance
Usually important
Usually not important

17. Types of viral infections
1) Asymptomatic infection ;
The majority of viral infections are subclinical
Acute infection ;
The majority of acute viral infections resolve
spontaneously.
Persistent infection ;
Some viruses persist for longer period ,
Ex.
Latent infections ;
. In those infections ,the patient recovers from the initial infection then virus enters the latent state in the neuron , and virus production stops, but can be reactivated at subsequent time and disease can occur.
Such as herpesvirus infections
Chronic infections ; .
. Ex. Chronic hepatitis B is Characterized
by the presence of hepatitis B virus in the blood for more than 6-months.

18. True or False True Viruses are transmitted only from person to person
Viral diseases can be
localized or systemic
All viral infections resolve spontaneously
Brain cannot be infected by virus
False
True

19. Viral diseases
Viruses can cause a wide spectrum of diseases, ranging from mild disease such as a common cold to severe disease as an encephalitis

20. Example of viruses causing skin rash
Varicella - Zoster Virus
Varicella : Chickenpox:
1o illness
Generalized vesicular rash
Starts on trunk , spread to face & limbs
Zoster: Shingles:
Recurrent form
Localized vesicular rash

21. Example of viruses causing skin rash
Measles Virus
maculopapular rash
appears first on the face
then spread downward
over the trunk and extremities

22. Viral Hepatitis - Historical Perspective
Enterically
transmitted
“Infectious” A E
Viral hepatitis
NANB
Parenterally
transmitted
“Serum” B D C
F, G,
? other 2

23. Fever , anorexia , nausea ,vomiting, and jaundice are typical
Viral Hepatitis presents a similar clinical picture. What ever the causative viruses
Fever , anorexia , nausea ,vomiting, and jaundice are typical
Jaundiced skin
Jaundiced sclera
Dark urine ,pale stool and elevated liver enzymes level are seen

24. Viral Hepatitis - Overview
Type of Hepatitis A B C D E
Source of
feces
blood/
blood/
blood/
feces
virus
blood-derived
blood-derived
blood-derived
body fluids
body fluids
body fluids
Route of
fecal-oral
percutaneous
percutaneous
percutaneous
fecal-oral
transmission
permucosal
permucosal
permucosal
Chronic no
yes
yes
yes no
infection
Prevention
pre/post-
pre/post-
blood donor
ensure safe
By preventing
HBV infection
exposure
exposure
screening;
drinking
immunization
immunization
risk behavior
& eating
modification 3

25. AIDS Acquired Immune Deficiency Syndrome
Transmission:
Clinical Features
The end stage of the disease
Caused by
two human retroviruses,
termed
human immunodeficiency virus
types 1 and 2
(HIV 1 & 2).
The course of HIV infection can be divided into three
stages:
1- The acute phase
2- The Latent phase
3-AIDS

26. Clinical Features
1- Acute Stage:
Mostly asymptomatic
Some patients have symptoms resembling
Infectious mononucleosis,
with or without aseptic meningitis or rash
2- Latent Stage:
Asymptomatic
≈ 8-10 years
Persistent Generalized Lymphadenopathy (PGL)
AIDS – related complex (ARC)
3- Late Stage : AIDS is the end stage of the disease characterized by:
Marked decrease in CD4 T-helper cells
Severe immunologic impairment
Opportunistic infections
Unusual cancers (Kaposi’s sarcoma)

27. Congenital infection
For example ;
Congenital Rubella

28. Viral Zoonoses Arthropod-borne Vs Non-arthropod borne zoonoses
Ex. Yellow Fever Virus
Ex. Rabies virus
Jungle Yellow Fever:
Vector: mosquito
Reservoir: Monkeys
Accidental host: humans
It is a disease of Monkeys
Urban Yellow Fever:
Vector: mosquito
Reservoir: human
It is a disease of humans

29. True or False Viruses can cause different types of skin rash
Viral hepatitis have a similar clinical picture
Chronic hepatitis can be caused by all viral hepatitis
AIDS is a virus
Viral infection during pregnancy doesn't harm infent
True
False

30. Treatment
Few antiviral drugs are selective enough to prevent viral replication without injury to the host .
Viruses are also not affected by antibacterial agents.
Management are available for certain infections;
For example,
Influenza infections
Herpesvirus infections
AIDS
( Combination drugs may effective in prolonging life & improving quality of life ,but doesn’t cure HIV infection
so treatment should be continued all life )
Chronic hepatitis B & C
( Prolonged treatment has succeeded in eliminating the hepatitis virus in some patients )

31. Control measures Such measures fall into two groups;
Individual measures;
Personal hygiene , especially
Hand washing
Personal behaviour , e.g.
Avoidance of injected drug
abuse & multiple sexual partners
Isolation of patients with
dangerous infection
Appropriate immunization for travellers
Community measures;
Surveillance of food /milk /water supplies & blood products
Maintenance of hygiene &
avoidance of overcrowding
Where appropriate , control of insect
vectors , and immunization of animals
Routine immunization programmes ;

32. Immunization Influenza Rotavirus Rabies Yellow fever
Prevention of viral diseases can be achieved by the use of vaccines & the administration of performed antibody.
Vaccines are available for certain viruses such as ;
Hepatitis A
Hepatitis B
MMR(Measles , Mumps & Rubella)
Varicella
Poliovirus
Influenza
Rotavirus
Rabies
Yellow fever

33. MCQ-1 Viruses have the following characteristics except one :
1-They range in size between 20 – 300 nm .
2-They contain one type of nucleic acid, either DNA or RNA .
3-They lack cellular organelles .
4-All have envelope.
5-They must replicate in cells.

34. MCQ-1 Viruses have the following characteristics except one :
1-They range in size between 20 – 300 nm .
2-They contain one type of nucleic acid, either DNA or RNA .
3-They lack cellular organelles .
4-All have envelope . False
5-They must replicate in cells.

35. MCQ-2
The following statements regarding viral hepatitis are false except one :
1-All are usually transmitted by blood and sexual contact .
2-All are have a similar clinical picture
3-All have vaccines.
4-All can cause chronic infection .
5-All resolve spontaneously .

36. MCQ-2
The following statements regarding viral hepatitis are false except one :
1-All are usually transmitted by blood and sexual contact .
2-All are have a similar clinical picture .TRUE
3-All have vaccines.
4-All can cause chronic infection .
5-All resolve spontaneously .

37. MCQ-3 The following statements regarding HIV are true except one :
1-It causes AIDS .
2-It is transmitted parenterally , sexually & perinatally.
3-Treatment should be continued all life.
4-Vaccine is available .
5-HIV infection can be divided into three stages .

38. MCQ-3 The following statements regarding HIV are true except one :
1-It causes AIDS .
2-It is transmitted parenterally , sexually & perinatally.
3-Treatment should be continued all life.
4-Vaccine is available . False
5-HIV infection can be divided into three stages .

39. MCQ-4
One of the following diseases is transmitted to human through the bite of animal :
1-Rabies.
2-Yellow fever .
3-AIDS .
4-Varicella .
5-Rubella .

40. MCQ-4
One of the following diseases is transmitted to human through the bite of animal :
1-Rabies.
2-Yellow fever .
3-AIDS .
4-Varicella .
5-Rubella .

41. MCQ-5
Viral infections can be controlled by following measures except ;
1- Avoidance of overcrowding
2- Avoidance of injected drug abuse
3- Avoidance of multiple sexual partners
4- Avoidance of viral vaccines
5- Hand washing

42. MCQ-5
Viral infections can be controlled by following measures except ;
1- Avoidance of overcrowding
2- Avoidance of injected drug abuse
3- Avoidance of multiple sexual partners
4- Avoidance of viral vaccines . FALSE
5- Hand washing

43. Thank you