Comparison of Morphology,Epidemiology,Classification,Genome structure and organisation,Prevention and treatment of DNA Viruses

1. Morphology Comparison of Parvovirus, Adenovirus, Poxvirus,
Papillomavirus, and Human Herpesvirus
These five virus families each have distinct morphologies:
1. Parvovirus:
● Structure: Smallest DNA virus, icosahedral capsid with 32 capsomeres, non-enveloped.
● Size: ~20-25 nm in diameter.
● Genome: Single-stranded DNA, linear or closed circular.
● Classification:
○ Subfamily: Parvovirinae
○ Genuses: Erythroparvovirus (B19), Bocavirus, Dependovirus
● Medically Important Species:
○ Human parvovirus B19 (Erythroparvovirus): causes fifth disease, aplastic crisis, fetal
hydrops.
○ Human bocavirus: associated with respiratory infections in children.

2. 2. Adenovirus:
● Structure: Icosahedral capsid with 252 capsomeres, non-enveloped, fibers projecting
from the vertices.
● Size: 70-90 nm in diameter.
● Genome: Double-stranded DNA, linear.
● Classification:
○ Genera: Mastadenovirus (human adenoviruses), Aviadenovirus, etc.
● Medically Important Species:
○ Human adenovirus serotypes 1, 2, 3, 4, 5, 7: cause respiratory infections,
conjunctivitis, gastroenteritis.
○ Serotypes 40, 41: cause keratoconjunctivitis.

3. 3. Poxvirus:
● Structure: Ovoid virion with an outer membrane and a thick lateral body containing the
core and DNA.
● Size: 200-300 nm in diameter.
● Genome: Double-stranded DNA, linear.
● Classification:
○ Subfamilies: Orthopoxvirinae (smallpox eradicated), Orthopoxvirus (monkeypox),
Capripoxvirinae, etc.
● Medically Important Species:
○ Variola virus (Orthopoxvirus): causative agent of smallpox (eradicated in 1980).
○ Monkeypox virus (Orthopoxvirus): causes monkeypox in humans and animals.
○ Vaccinia virus (Orthopoxvirus): used in the smallpox vaccine.

4. 4. Papillomavirus:
● Structure: Icosahedral capsid with 72 capsomeres, non-enveloped.
● Size: ~50 nm in diameter.
● Genome: Double-stranded DNA, circular.
● Classification:
○ Genera: Alphapapillomavirus (high-risk for cancer), Betapapillomavirus (low-risk for
cancer), Gammapapillomavirus, etc.
● Medically Important Species:
○ HPV 16, 18, 31, 33, 45, 52, 58: high-risk for cervical, head and neck, and other
cancers.
○ HPV 6, 11: low-risk for genital warts and recurrent respiratory papillomatosis.

5. 5. Human Herpesvirus:
● Structure: Icosahedral capsid with 162 capsomeres, enveloped with glycoprotein spikes.
● Size: 120-200 nm in diameter.
● Genome: Double-stranded DNA, linear.
● Classification:
○ Subfamilies: Alphaherpesvirinae (HSV-1, HSV-2), Betaherpesvirinae (CMV, EBV),
Gammaherpesvirinae (HHV-6, HHV-7), Deltaherpesvirinae (HHV-8)
● Medically Important Species:
○ HSV-1: causes cold sores (orofacial herpes), encephalitis.
○ HSV-2: causes genital herpes.
○ CMV: associated with congenital CMV infection, mononucleosis, retinitis.
○ EBV: associated with infectious mononucleosis, nasopharyngeal carcinoma, Burkitt's
lymphoma.
○ HHV-6: associated with exanthema subitum (roseola), febrile seizures.
○ HHV-7: associated with pityriasis rosea, febrile seizures.
○ HHV-8: associated with Kaposi sarcoma, primary effusion lymphoma.

6. Here's a table summarizing the key morphological features:
Virus Family Capsid
Geometry
Enveloped Size Genome
Parvovirus Icosahedral No 20-25 nm Single-stranded
DNA, linear or
closed circular
Adenovirus Icosahedral No 70-90 nm Double-stranded
DNA, linear
Poxvirus Ovoid Yes 200-300 nm Double-stranded
DNA, linear
Papillomavirus Icosahedral No 50 nm Double-stranded
DNA, circular
Human
Herpesvirus
Icosahedral Yes 120-200 nm Double-stranded
DNA, linear
Genome Structure and Organization
Virus Genome
Type
Size (kb) Structure Organizatio
n
Notable
Features
Parvovirus
B19
Single-strand
ed DNA
5.6 Linear Non-coding
terminal
regions flank
two
palindromic
inverted
repeats
containing
genes for
early
(nonstructural
) and late
(structural)
proteins.
Ambisense
replication
(reads in both
directions
from
palindromes)

7. Adenovirus Double-stran
ded DNA
28-40 Linear Inverted
terminal
repeats flank
a central
region with
early
(regulatory)
and late
(structural)
genes
organized in
blocks.
Terminal
repeats
facilitate
integration
into host
genome
(non-integrati
ng for some
types)
Poxvirus Double-stran
ded DNA
130-230 Linear Inverted
terminal
repeats flank
a central
region with
genes for
viral core,
early
(transcription
, DNA
replication),
and late
(structural)
proteins.
Large,
complex
genome with
extensive
non-coding
regions and
gene
clustering
Papillomavir
us (HPV)
Double-stran
ded DNA
7-8 Circular Non-coding
long control
region (LCR)
flanked by
early (E) and
late (L)
protein-codin
g regions. E
genes
regulate
replication
and L genes
encode
Circularity
due to hairpin
termini; E6
and E7
oncogenes in
LCR

8. structural
proteins.
Human
Herpesvirus
(e.g., HSV-1)
Double-stran
ded DNA
125-175 Linear Two unique
long (L)
segments
flanked by
short (S)
segments; L
segments
contain genes
for all
nonstructural
and most
structural
proteins; S
segments
encode
immediate-ea
rly genes for
reactivation.
Large,
complex
genomes with
significant
variation
between
types; latency
with periodic
reactivation
Viral Culture
Virus Culturability Culture
Cells
Specific
Requirement
s
Additional
notes
CPE
Parvovirus
B19
Difficult Fetal bone
marrow or
erythroid
progenitor
cells
Complex
media;
co-cultivation
with host
cells;
extended
incubation
(weeks)
Limited
sensitivity;
primarily for
research
None
observed

9. Adenovirus Easy Epithelial cell
lines (e.g.,
HeLa,
HEK-293)
Standard
culture media
Fast-growing;
cytopathic
effect (CPE)
visible in
days
Rounding,
detachment,
syncytia
formation
Poxvirus
(e.g., Variola
Major)
Easy Embryonic
fibroblast cell
lines (e.g.,
BGMK)
Specific
media with
antibiotics;
optimal
temperature
Characteristic
pock lesions
formation on
cell
monolayer
Large, dense
plaques with
eosinophilic
inclusions
Papillomavir
us (HPV)
Difficult Differentiated
epithelial
cells (e.g.,
keratinocytes
)
Specialized
media with
low oxygen;
lengthy
incubation
(weeks to
months)
Requires
precise
conditions
and expertise;
limited
success
No typical
CPE
Human
Herpesvirus
(e.g., HSV-1)
Easy Epithelial cell
lines (e.g.,
Vero,
MRC-5)
Standard
culture media
CPE with
characteristic
plaques after
several days
Rounding,
enlargement,
ballooning,
syncytia
formation;
intranuclear
inclusions

10. Replication
Virus Family Stage 1:
Attachment
& Entry
Stage 2:
Uncoating &
Early Gene
Expression
Stage 3:
DNA
Replication
& Late Gene
Expression
Stage 4:
Assembly &
Maturation
Stage 5:
Release
Parvovirus Binds to
P-selectin
receptor.
Enters by
endocytosis
or direct
penetration.
Uncoating in
cytoplasm.
Early genes
code for
non-structural
proteins
involved in
DNA
replication.
Viral DNA
replicates via
rolling-circle
replication in
nucleus. Late
genes code
for capsid
proteins.
Capsid
assembly in
nucleus. New
virions bud
through inner
nuclear
membrane.
Virions
released
through
lysosomal
lysis or cell
death.
Adenovirus Binds to
coxsackieviru
s and CAR
receptors.
Enters by
endocytosis.
Uncoating in
nucleus.
Early genes
code for
proteins for
DNA
replication
and late gene
expression.
Viral DNA
replicates via
rolling-circle
replication in
nucleus. Late
genes code
for structural
and
non-structural
proteins.
Capsid
assembly in
nucleus. New
virions
packaged into
pre-existing
host cell
vesicles and
released by
exocytosis.
Poxvirus Binds to
glycosaminog
lycans and
other
receptors.
Enters by
fusion with
plasma
membrane or
endocytosis.
Uncoating in
cytoplasm.
Early genes
code for
proteins for
DNA
replication
and late gene
expression.
Viral DNA
replicates via
rolling-circle
replication in
cytoplasm.
Late genes
code for
structural and
non-structural
proteins.
Capsid
assembly in
cytoplasm.
New virions
bud through
modified host
cell
membranes
and acquire
envelope.
Virions
released by
cell lysis or
exocytosis.

11. Papillomavir
us
Binds to
heparan
sulfate
proteoglycans
and integrins.
Enters
through
clathrin-medi
ated
endocytosis.
Uncoating in
nucleus.
Early genes
code for
proteins for
DNA
replication
and control of
host cell
cycle.
Viral DNA
replicates
episomally in
nucleus. Late
genes code
for capsid
proteins.
Capsid
assembly in
nucleus and
cytoplasm.
New virions
released
through cell
death or lysis.
Human
Herpesvirus
(HSV-1/2)
Binds to
heparan
sulfate and
glycoprotein
receptors.
Enters by
fusion with
plasma
membrane or
endocytosis.
Uncoating in
nucleus.
Early genes
code for
proteins for
DNA
replication
and late gene
expression.
Viral DNA
replicates via
rolling-circle
replication in
nucleus. Late
genes code
for structural
and
non-structural
proteins.
Capsid
assembly in
nucleus. New
virions bud
through inner
nuclear
membrane
and acquire
envelope.
Virions
released by
exocytosis or
cell death.
Human
Herpesvirus
(CMV)
Binds to
heparan
sulfate and
CD138
receptors.
Enters by
fusion with
plasma
membrane or
endocytosis.
Uncoating in
nucleus.
Early genes
code for
proteins for
DNA
replication
and late gene
expression.
Viral DNA
replicates via
rolling-circle
replication in
nucleus. Late
genes code
for structural
and
non-structural
proteins.
Capsid
assembly in
nucleus. New
virions bud
through inner
nuclear
membrane
and acquire
envelope.
Virions
released by
exocytosis or
cell death.
Human
Herpesvirus
(EBV)
Binds to
CD23 and
EBV
receptors.
Enters by
fusion with
plasma
Uncoating in
nucleus.
Early genes
code for
proteins for
DNA
replication
Viral DNA
replicates via
rolling-circle
replication in
nucleus. Late
genes code
for structural
Capsid
assembly in
nucleus. New
virions bud
through inner
nuclear
membrane
Virions
released by
exocytosis or
cell death.

12. membrane or
endocytosis.
and late gene
expression.
and
non-structural
proteins.
and acquire
envelope.
Epidemiology
Virus Family Transmissio
n
Reservoir Seasonality Prevalence Pathogenesis
Parvovirus
(B19)
Respiratory
droplets,
close contact,
vertical
(mother to
fetus)
Humans No clear
seasonality
Widespread;
most infected
by adulthood
Adenovirus Respiratory
droplets,
contact with
contaminated
surfaces,
fecal-oral
route
Humans and
some animals
More
common
winter/early
spring
Widespread;
most exposed
to multiple
serotypes by
adulthood
Respiratory
illness,
conjunctivitis
,
gastroenteriti
s; more
severe in
young
children and
elderly
Poxvirus
(Smallpox
eradicated)
Respiratory
droplets
Humans
(eradicated)
N/A
(eradicated)
N/A
(eradicated)
Fatal fever,
rash, and
pustules
(eradicated in
1980)

13. Poxvirus
(Monkeypox
)
Close contact
with infected
animals or
humans
Animal
reservoirs
(rodents)
No clear
seasonality
Rare and
localized
outbreaks
Fever, rash,
pustules
Papillomavir
us (HPV)
Skin-to-skin
contact,
including
sexual
contact
Humans;
virtually
everyone
infected with
at least one
type by
adulthood
No clear
seasonality
Extremely
high; almost
all sexually
active
individuals
ever infected
with some
type
Warts,
cervical
cancer, other
cancers
(high-risk
types)
Human
Herpesvirus
(HSV-1,
HSV-2)
Close contact
(oral or
genital)
Humans;
lifelong latent
infection
common
No clear
seasonality
for primary
infections
Very high;
most
individuals
have latent
HSV-1 by
adulthood
Cold sores,
genital herpes
Human
Herpesvirus
(CMV)
Bodily fluids
(saliva, urine,
etc.)
Humans;
lifelong latent
infection
common
No clear
seasonality
Very high;
most
individuals
have latent
CMV by
adulthood
Congenital
CMV
infection,
mononucleosi
s, retinitis
Human
Herpesvirus
(EBV)
Bodily fluids
(saliva, etc.)
Humans;
lifelong latent
infection
common
No clear
seasonality
for primary
infections
Very high;
most
individuals
have latent
EBV by
adulthood
Infectious
mononucleosi
s,
nasopharynge
al carcinoma,
Burkitt's
lymphoma

14. Viral Pathogenesis
Virus Portal of
Entry
Mechanism
of
Pathogenesis
Incubation
Period
Diseases
Caused
Portal of
Exit
Parvovirus
B19
Respiratory
tract (via
inhalation),
placenta
(transplacenta
l)
Replicates in
red blood cell
precursors,
leading to
anemia and
fetal damage.
4-21 days Fifth disease
(erythema
infectiosum),
aplastic
anemia (rare),
hydrops
fetalis
(transplacenta
l), fetal
anemia
None (acute
infection)
Adenovirus Respiratory
tract (via
inhalation),
conjunctiva
(eye contact),
gastrointestin
al tract
(oral-fecal)
Replicates in
epithelial
cells, causing
cell lysis and
inflammation
.
2-14 days Common
cold,
pharyngitis,
conjunctivitis
,
gastroenteriti
s, pneumonia,
cystitis
Respiratory
tract
(coughing,
sneezing),
conjunctiva
(tears), feces
Poxvirus
(e.g., Variola
Major)
Skin (direct
contact),
respiratory
tract
(inhalation)
Replicates in
epithelial
cells, causing
cell lysis and
inflammation
. Spreads to
lymph nodes
and
bloodstream,
causing
systemic
infection.
7-14 days Smallpox
(now
eradicated),
monkeypox,
cowpox
Skin lesions
(pustules)

15. Papillomavir
us (HPV)
Skin and
mucosal
surfaces
(sexual
contact,
non-sexual
skin-to-skin
contact)
Replicates in
epithelial
cells, causing
uncontrolled
cell
proliferation
and potential
transformatio
n into cancer.
Several
weeks to
years
Warts
(common,
genital,
plantar),
cervical
cancer, head
and neck
cancers
Skin lesions,
shed
epithelial
cells
Human
Herpesvirus
(e.g., HSV-1)
Mucosal
surfaces
(eyes, mouth,
genitals)
Replicates in
epithelial
cells and
establishes
latency in
sensory
ganglia.
Reactivation
under stress
can cause
recurrent
lesions.
2-21 days
(primary
infection),
variable
(reactivation)
Cold sores
(HSV-1),
genital herpes
(HSV-2),
chickenpox
(VZV),
shingles
(VZV
reactivation)
Vesicles,
saliva, genital
secretions
Prevention and Treatment of Parvovirus, Adenovirus, Poxvirus,
Papillomavirus, and Human Herpesvirus
Virus Prevention Treatment
Parvovirus B19 No specific vaccine;
Handwashing; Avoiding
high-risk contacts (pregnant
women,
immunocompromised
individuals)
Supportive care for symptoms
(e.g., pain relievers, fluids);
Immune globulin for pregnant
women at risk of fetal
infection
Adenovirus Frequent handwashing;
Avoiding sick individuals;
Supportive care for symptoms
(e.g., pain relievers, rest,

16. Vaccines for some serotypes
(e.g., military); Good hygiene
practices
fluids); Antivirals for severe
cases (rare)
Poxvirus (e.g., Variola
Major)
Eradicated through global
vaccination (Smallpox);
Animal poxviruses may
require specific measures
based on type
Supportive care for
symptoms; Antivirals for
specific types (e.g., cidofovir)
Papillomavirus (HPV) Vaccination available for
certain high-risk types; Safe
sex practices; Regular
cervical cancer screening
Removal of visible warts
(cryotherapy, lasers); Vaccine
(Gardasil 9) protects against
most HPV types causing
cervical cancer and genital
warts
Human Herpesvirus (e.g.,
HSV-1, HSV-2)
No vaccine for common
types; Safe sex practices;
Avoiding close contact with
lesions; Good hygiene
Antivirals for symptomatic
relief and to reduce
transmission; Pain relievers;
Topical agents for skin
lesions