This document provides information on viruses including their structure, classification, life cycles, and examples of common viral diseases. It defines key terms like capsids, genomes, and envelopes. It describes the four main types of viral structures: helical, icosahedral, enveloped, and complex. It covers taxonomy and the bases for viral classification such as host range, size, and antigenic properties. Examples are given of major viral families that infect animals like Herpesviruses, Hepadnaviruses, Retroviruses, Arenaviruses, Flaviviruses, and more.

1. Choose me !!!!!!
Virology
Morphology & Background
Common viruses
Viral Diseases

2. Background Information:)
s virus are parasites, s all cells can be
not cells parasitized by
s virus are packages virus, they only
of genetic info - attack closely
nucleic acids in related organisms
protein coats s virus comes from a
s virus only supplies latin word “poison”
information, rest is or “slime”
dependent on host

3. What are viruses? 
s virus = “poison”
s with genetic material (DNA or RNA) and
protein coat (capsid).
s obligatory intracellular parasites.
s infect the cells of a biological organisms.
s they replicate by using the host cell’s
metabolic“machinery”.

4. Definition of Terms: 
s Capsid- protein shell, or coat, that
encloses the nucleic acid genome
s Capsomere – Morphologic units of virus
seen under the EM on the surface of
icosahedral virus particles
• Represents clusters of polypeptide
s Defective virus – virus particle that is
functionally deficient in some aspect of
replication

5. More terms: 
s Envelope – lipid containing membrane
that surrounds some virus particles
• Acquired during viral maturation by a
budding process thru a cellular membrane
s Nucleocapsid – protein nucleic acid
complex representing the packaged
form of the viral genome
s Subunit – single folded viral polypeptide
chain

6. s Structural units – Basic protein building
blocks of the coat.
• Usually a collection of more than one
nonidentical protein unit.
• The structural unit is often referred to a
protomer.
s Virion – Complete virus particle. In
some instances, the virion is identical to
the nucleocapsid. In more complex
virions, this includes the nucleocapsid
plus a surrounding envelope.

7. Background Information: 
s Dmitri Iwanowski - s Are viruses alive??
1892 first isolation they contain
of TMV macromolecules
s Martinus Beijerinck but does not
- filterable viruses reproduce directly
s Wendell Stanley - --- virions are
intact, non-
1935 purified &
replicating virus
crystallized TMV
particles ( no life)

8. Basis of classification
s Virus morphology s Virus genome
• Size properties
• Shape • Nucleic Acid ( DNA
• Type of symmetry or RNA )
• Presence & absence • Size of genomes in
of peplomers kb (kilobase pairs )
• Presence & absence • Strandedness (single
of membranes or double )
• Nucleotide sequence

9. Basis for Classification:
s Host Range s Size
• Plant virus • 25 nm to 300 nm
• Animal Virus • 1/10 to 1/3 of
• Bacteriophage bacteria
• no cytoplasmic
• Specificity cultivars structures
( plants), race or • can be 77 genes
strains, receptors or 3 genes but
(protein) still very lethal

10. SIZE
s Most viruses with capsid = between 10-300 nm

11. Structure:
s Nucleic Acid core
surrounded by
protein
s Viral Envelope -
naked or
enveloped
s Nucleic Acid -
DNA or RNA

12. s Genome
organization &
replication s Antigenic properties
• Gene order
• Gene number
s Biologic properties
• Position of open
including :
reading frames • Natural host range
• Patterns of • Mode of
replication transmission
• Cellular sites • Vector relationship
• Pathogenecity
• Tissue tropisms
• Pathology

13. s Physiochemical s Virus protein
Properties of the properties
virion • Number
• Molecular mass • Size
• Buoyant density • Functional activities
• pH stability • Amino acid
• Thermal stability sequence
• Susceptibility to agents • Modifications &
– Ethers special functions
– Detergents – Transcriptase
– Reverse trans.
– Neuramidase
– fusion

14. Types of Structure
s Four morphological types:
• 1. Helical Viruses
• 2. Icosahedral viruses
• 3. Enveloped viruses
• 4. Complex viruses

15. Helical virus
-Resemble long rods, may be rigid or flexible
-Viral nucleic acid found within a hollow cylindrical capsid.
-with single type of protomers stacked around a central
axis to form a tube; eg. Tobacco mosaic virus.

16. Icosahedral
spherical appearance
but capsomeres
arranged in a
geometrical pattern like
a soccer ball;
eg.hepatitis B

17. Enveloped
with outer lipid layer = viral envelope

18. Complex
-- with extra
structure such as
protein tails,
complex outer
walls; eg.
Bacteriophages,
Poxviruses.

19. Life Cycle:
s outside the host there is no replication
s Stages :
• -->Adsorption
• --> Penetration
• --> Uncoating
• --> Viral synthesis
• --> Maturation
• --> Release

20. Multiplication of Viruses
s Lytic cycle – ends with the lysis and
death of the host cell.
s Lysogenic cycle- host cell remains alive

22. Taxonomy:
s ICTV - International Committee on
Taxonomy of Virus
s Family Name -- Viridae -- Retroviridae
s Genus -- Virus -- Lentivirus
s Specie -- English -- HIV
s Hepadnaviridae -- 7 DNA - Hepatitis

23. Misc. Information:
s Replication applicable to all virus
s Plaque count - PFU Plaque forming
units
s One Step Growth Phase -- Latent --->
Burst Period

24. Common viruses in animals:
s Line 1 - Family
s Line 2 - Classification based on N.A.
s Line 3 - Properties
s Line 4 - Virus (species or Genus)
s Line 5 - Diseases
*** Legend

25. s Herpesviridae
s DNA virus
s Enveloped dsDNA
s Herpes simplex 1&2,
Varicella zoster, EBV,
cytomegalovirus CMV
s cold sores, genital
herpes, shingles,
mononucleosis, birth
defects

26. s Poxviridae
s DNA virus
s Enveloped dsDNA
s Smallpox virus
s Smallpox ( variola )

27. s Hepadnaviridae
s DNA virus
s Enveloped dsDNA
s Hepatitis B virus
s Hepatitis B

28. New Nomenclature for
Hepatitis Virus
s Hepatitis A
• HAV virus
• Etiologic agent of infectious Hepatitis
• A picornavirus, the prototype of a new
genus, Hepatovirus
• Anti-HAV – antibody to HAV. Detectable at
onset of symptoms; lifetime persistence
• IgM antibody

29. Hepatitis B
s Antibodies for Hep B
s HBV- Hepatitis B • Anti-HBs
virus • Anti-HBe
s Etiologic agent of • Anti-HBc
serum hepatitis
s A hepadnavirus • IgM class Antibody
s HBsAg, HBeAg,
HBcAg

30. Hepatitis C
s HCV – Hepatitis C Virus
s A common etiologic agent of post
transfusion hepatitis
s A Flavivirus, genus Hepacivirus
s Anti-HCV – antibody to HCV

31. Hepatitis D
s Hepatitis D Virus
s Etiologic agent of delta hepatitis
s Causes infection only in presence of
HBV
s HDAg – Delta antigen, detectable only
in early acute HDV infection
s Anti-HDV - Antibody

32. Hepatitis E
s HEV – Hepatitis E Virus
s Enterically transmitted hepatitis virus
s Causes large epidemics in Asia, North
& West Africa and Mexico
s Fecal-oral or waterborne infection
s Unclassified

34. s Papoviridae
s DNA virus
s naked dsDNA
s Human papillomaviruses
s Warts

35. Polyomaviruses
s Small (45nm ) naked, heat stable, ether
resistant virus
s Cubic symmetry with 72 capsomeres
s Circular, double stranded DNA
s JC virus, BK virus, SV40 virus
s Formerly part of Papoviridae family

36. s Adenoviridae
s DNA virus
s Naked dsDNA
s Human adenovirus
s respiratory, enteric
diseases,
infectious pinkeye

37. Parvovirus
s Naked Single stranded DNA virus
s Cubic symmetry with 32 capsomeres
s 5.6 kb in size
s Requires the presence of adenovirus or
herpesvirus as helper ( defective )

38. s Retroviridae
s RNA virus
s Enveloped + strand RNA
s HIV-1 & 2, HTLV-1 &2
s AIDS , T cell leukemia

39. Life Cycle of HIV Virus

40. Astroviruses
s 28-30 nm in diameter
s Exhibit a distinctive star-like morphology
under the EM
s Ss + sense RNA, 6.4 – 7.4 kb in size
s Causes diarrheal illnesses
s Transmitted by fecal-oral route thru
contaminated food or water

41. Arboviruses (arthropod borne)
s Arenaviridae
s Bunyaviridae
s Flaviviridae
s Filoviridae
s Reoviridae
s Togaviridae

42. Arenaviruses
s Generally associated with rodent-
transmitted disease in humans.
s Each virus usually is associated with a
particular rodent host species in which it
is maintained
s Divided into two groups:
• the New World or Tacaribe complex
• the Old World or LCM/Lassa complex.

43. Filoviruses

44. s Flaviviridae
s RNA virus
s enveloped +
strand RNA
s Yellow & Dengue
fever , Hep C
virus
s Yellow & Dengue
fever, Hepatitis C

45. Prevention of Dengue

46. Types of Dengue
s Non-fatal dengue fever (DF)
s Fatal Dengue Hemorrhagic fever (DHF)
s Dengue Shock Syndrome ( DSS)

47. Serotypes of Dengue
s 4 serotypes
s DEN-1, DEN-2, DEN-3, DEN-4
s DEN-2 shows greatest antigenic and
genotypic distance from the others
s Protective immunity after infection is
homotypic
(Which means if your really unlucky u can
have dengue __ times.) 

48. More types of Flavivirus
s Eastern & Western Encephalitis
s St. Louis Encephalitis
s West Nile Fever
s Japanese B Encephalitis
s Yellow Fever

49. s Reoviridae
s RNA virus
s naked dsRNA
s Rotavirus
s Infant diarrhea

50. s Bunyaviridae
s RNA virus
s Enveloped - strand
RNA
s Hantavirus
s Respiratory
distress syndrome

51. s Togaviridae
s RNA virus
s Enveloped +
strand RNA
s Alphavirus, Rubella
virus
s encephalitis,
Rubella (German
measles)

52. Picornaviruses
s Enterovirus s Rhinovirus
• Transient inhabitants • Isolated chiefly from
of the human the throat and nose
alimentary tract • More than 100
• Poliovirus species based on
• Coxsackie virus receptors
– ICAM -1
• Paraechovirus
– LDLR
– Echovirus 22
– Echovirus 23

53. s Picornaviridae
s RNA virus
s Naked + strand RNA
s Enterovirus, Poliovirus,
echovirus, Rhinovirus,
hepatitis A virus
s Polio, Myocarditis,
pericarditis, colds,
Hepatitis A

54. s Coronaviridae
s RNA virus
s Enveloped +
strand RNA
s Coronavirus
s upper respiratory
tract infections

55. s Calciviridae
s RNA virus
s naked + strand
RNA
s Norwalk Agents
s Gastroenteritis

56. s Orthomyxoviridae
s RNA virus
s Enveloped - strand RNA
s Influenza virus
s Influenza

57. s Rhabdoviridae
s RNA virus
s enveloped - strand
RNA
s Rabies virus
s Rabies

58. s Paramyxoviridae
s RNA virus
s enveloped - strand
RNA
s Mumps, measles virus,
Parainfluenza virus,
Respiratory syncitial vir.
s mumps, rubeola,
Croup, Bronchiolitis

59. Recent Viral Diseases
s SARS- severe acute respiratory syndrome

60. Avian Flu- spread of H5N1 strain

61. Influenza Pandemic
(1918-1919)
– TEM of Spanish Influenza Virus
(negatively-stained); subtype H1N1;
H2N2; H3N2
25 million deaths in 25 weeks
20% of world population affected.
1957-1958
1968-1969
Next pandemic ????

62. Virus entry into an animal cell

63. What other roles could be
attributed to viruses other than
being pathogens?
s Basic research, molecular biology and
biotechnology
s Horticulture
s Cross- protection
s Gene therapy
s Phage therapy
s Viro-therapy

64. Continuation……..
s Material Science and Nanotechnology- In April 2006,
MIT scientists created nanoscale metallic wires using
a genetically-modified virus. The MIT team was able
to use the virus to create a working battery with an
energy density up to three times more than current
materials. The potential exists for this technology to
be used in liquid crystals, solar cells, fuel cells, and
other electronics in the future.
s Biological warfare- synthesis/recreation of viruses in
laboratory (eg. 1918 flu virus, smallpox virus- Variola
major)