This document provides information on several families of DNA viruses that infect humans. It discusses the Hepadnaviridae, Parvoviridae, Papillomaviridae, Polyomaviridae, Adenoviridae, Herpesviridae, Poxviridae families. For each family it provides details on virion structure, genome structure, examples of diseases caused. It also summarizes replication strategies of different DNA viruses depending on whether they replicate in the nucleus or cytoplasm. The document discusses adenoviruses in more depth covering morphology, antigenic structure, classification, assembly, cytopathic effect, pathogenesis and clinical syndromes. It also discusses papillomaviruses, polyomaviruses, her

1. D
N
A-CO
N
SIST
VIR
USES

2. Classification of DNA viruses that infect human
Family Virion
structure
Genom structure Characteristics
Hepadnaviridae lipid-contain.
envelope
1 molecule, mainly
ds DNA but with a
single strand gap
Hepatitis B virus
Parvoviridae Non-
enveloped
1 molecule,
ss DNA
outbreaks of gastroenteritis
following eating of shellfish
Papillomaviridae
Polyomaviridae
Non-
enveloped
1 molecule, circular
ds DNA
human papilomaviruses
(genital and oral carcinomas)
Adenoviridae Non-
enveloped
1 molecule, ds
DNA
Human: infections of respira-
tory and the intestinal tracts,
of the eyes; Animals: tumors
Herpesviridae enveloped
with surface
projections
1 molecule,ds DNA herpes simplex virus,
cytomegalovirus
Poxviridae enveloped;
large, brick-
shaped
ds DNA, covalently
closed ends
smallpox virus, vaccinia
virus

3. DNA VIRUS REPLICATION STRATEGIES
Viral genomes contain information which:
ensures replication of viral genomes
ensures packaging of genomes into virions
alters the structure and/or function of the host cell to a greater or lesser degree
VIRAL STRATEGY
Viral strategy refers to the manner in which each virus carries out the above
functions. Since a virus is an intracellular parasite, it has to operate within
limits imposed by the host cell, or circumvent these limitations.
General
The virus needs to make mRNAs that can be translated into protein by the host
cell translation machinery.
The virus needs to replicate its genome.
Host enzymes for mRNA synthesis and DNA replication are nuclear (except for
those in mitochondrion) and so, if a virus is to avail itself of these enzymes, it
needs to enter the nucleus.

4. Nuclear DNA viruses
Parvoviridae
Papillomaviridae
Polyomaviridae
Adenoviridae
Herpesviridae
Cytoplasmic DNA viruses
Poxviridae
This means that they must provide their own mRNA and DNA
synthetic machinery.

5. PAPILLOMAVIRUS FAMILY
The Papillomavirus family was
formerly grouped with the
Polyomavirus family into the
Papovavirus family (PApilloma,
POlyoma, simian VAcuolating virus 40)
because members of both families have
a similar structure.
However, it is now clear that the two
families have a very different
replication strategy and so each group
has now been given its own family
status
PROPERTIES OF
POLYOMAVIRUSES AND
PAPILLOMAVIRUSES
They are small: 40 - 60nm
They are icosahedral: major
capsid protein is VP1, with
lesser amounts of VP2, VP3
They are non-enveloped
They have circular, double-
stranded DNA is associated
with cell histones (nucleosomes
)Papilloma virus

6. POLYOMAVIRUSES
These include SV40, BK, JC and
polyoma viruses.
All have a similar strategy for
DNA replication.
They are small (~40nm
diameter), icosahedral, non-
enveloped viruses that replicate
in the nucleus. Depending on the
host cell, they can either
transform the cell or replicate
the virus and lyze the cell.
SV40 virus, a polyoma virus

7. ADENOVIRUSES
got their name from the
adenoidal tissues
(tonsils) in which they
were first identified (in
1953 W.Rowe and
collaborators).

8. MORPHOLOGY
Size – 70-90 nm
Shape - icosahedral. Their
morphogenesis occurs in the cell
nucleus, where they also
aggregate to form large crystals
Their genome is a linear, ds
DNA
Type of symmetry - cubic
Naked.
Capsid consist of 252 capsomers

9. ANTIGENIC STRUCTURE OF
ADENOVIRUSES
4 soluble antigens are known
Hexon – A antigen –common
for all serotypes, is the main
structural protein of virion
(51%)
Penton – B antigen – causes
early toxic effect of
adenoviruses to the tissue
culture (9 % of all proteins of
virion)
Appendix, filament – C
antigen – causes
agglutination of erythrocytes
(5 %)
P antigen – inner protein –
releases after destroying of
the virion

10. CLASSIFICATION
Family Adenorividae
genera:1 Mammaliadenovirus
embracing adenoviruses of humans and mammals
species:49 pathogenic for human;
24 – for monkey;
9 – for cattle;
2-6 - for horses, sheep, dogs, mice
2 Aviadenovirus including adenoviruses of birds.
species: 9 pathogenic for cheek;
3 – for goose
3 –for turkey-cock
About 130 species (serotypes) of adenoviruses are known

11. ASSEMBLY
Assembly of adenovirus particles occurs in the nucleus.
DNA enters the particles after immature capsids are formed. The
capsids then undergo a maturation process, after which the cells
lyse and virions leak out.
More structural proteins are made than are needed and excess
structural proteins accumulate in the nucleus where they form
inclusion bodies.
Adenoviruses code for their own DNA polymerase and DNA
packaging proteins.
However, although adenoviruses code for their own DNA
polymerase, they use host factors in addition to viral proteins for
DNA replication, and they use host RNA polymerase and RNA
modification systems and so nucleic acid synthesis needs to be in
the nucleus.

12. Diagrammatic representation of the uptake
and uncoating of adenovirus particles.
Adapted from Zinsser Microbiology 20th Ed.

13. CLASSIFICATION ACCORDING TO THE
ANTIGENIC STRUCTURE (TO THE ABILITY
TO AGGLUTINATE THE RED BLOOD CELLS)
1 subgroup – adenoviruses, which agglutinate monkey’s
erythrocytes (3,7,11,14,16,20,21,25,28)
2 subgroup – adenoviruses which agglutinate white rat’s
erythrocytes completely
(8,9,10,13,17,19,22,23,24,27,29,30)
3 subgroup – adenoviruses which agglutinate white rat’s
erythrocytes partially
(1,2,4,5,6,12,18,31)

14. CLASSIFICATION ACCORDING TO THE
ONCOGENIC-ABILITY
Subgroup A – greatly oncogenic (types 12,18,31)
Subgroup B weakly oncogenic (types 3, 43, 7, 8, 11, 14,
16, 21)
Subgroup C and D – non oncogenic ( all other types)

15. CULTIVATION
- grow in tissue cells of human beings, monkeys and
other animals.
Most susceptible are subinoculated epithelial cells НеLа,
КВ, Нер-2, etc., in which the cytopathogenic effect is
relatively manifest. The inoculated tissue culture are
incubated at 37º C for 14 days.
- Are non pathogenic for laboratory animals
- Do not grow on chick embryo membranes.

16. CYTOPATHOGENIC EFFECT
The process of cell degeneration
consists of two phases.
During the first phase changes in
the cells are induced by toxin-
like factors (initial phase of
degeneration), while in the
second phase viruses multiply
within the nucleus and
cytoplasm (final phase of
degeneration).
Inclusion bodies from within the
nucleus. They consist of virions
which produce aggregates of
crystalline structure. Adenovirus
multiplication is accompanied by
accumulation of excess lactic
acid in the tissue culture.
Normal (not infected) НеLа cells (1);
cytopathic effect of adenoviruses on
HeLа cells (2)

17. PATHOGENESIS AND CLINICAL
PICTURE
Adenoviruses cause a variety of diseases, which may occur
singly or concurrently. The most important are infections of the
upper (sometimes lower) respiratory tracts, the eyes, and the
intestinal tract.
Adenoviruses can persist for months in the regional lymph nodes
or tonsils until they are reactivated.
The clinical picture of the disease does not strictly depend upon
the type of adenovirus. One and the same variant may produce a
wide variety of forms of the disease. The ability of various
serovars to produce one the same disease has also been
ascertained.

18. Infections of the respiratory tract take the form of rhinitis or
abacterial pharyngitis, depending on the virus type as well as
presumably on the disposition of the patient.
The eye infections may occur alone but are often concurrent with
pharyngitis, range from follicular conjunctivitis to a form of
keratoconjun-ctivitis that may even cause permanent partial loss
of eyesight.
The intestinal infections
An important aspect of the intestinal infections is that the primary
gastroenteritis forms are caused by the viral strains 40 and 41,
which are difficult to culture.

19. ADENOVIRUS- CLINICAL SYNDROMES (COMPILED)
Clinical
syndrome
Features Serotypes
commonly
involved
Serotypes
rarely
involved
URI Coryza, pharyngitis, tonsillitis, fever 1, 2, 3, 5, 7 4, 6, 11, 18,
21, 29, 30
Pharyngo-
conjunctival
fever
Fever, conjunctivits, pharyngitis,
headache, rash, lymphadenopathy
3, 4, 7, 14 1, 11, 16, 19,
37
LRI Bronchitis, pneumonia, fever, cough 3, 4, 7, 21 14, 1, 2, 5, 35
Pneumonia Fever, respiratory distress, cough,
severe in young children and infants
7 1, 2, 3,4, 14,
21, 7b
Pertussis-like
Syndrome
Fever, paroxysmal cough, post-
tussive vomiting
5 1, 2, 3, 12, 14,
19, 21, 35
Acute
Respiratory
Disease
Tracheobronchitis, pneumonia, fever;
epidemics in military recruits
4, 7 2, 3, 5, 8, 11,
14, 21

20. ADENOVIRUS- CLINICAL SYNDROMES (COMPILED)
Epidemic
Keratocon-
junctivitis
Headache, conjunctivitis
followed by keratitis,
preauricular lymphnodes
8, 19,
37
2-7, 14, 15,
19, 37
Acute
follicular/
Hemorrhagic
conjunctivitis
Chemosis, follicles,
subconjunctival hemorrhage,
preauricular lymph nodes
11
Acute
Hemorrhagic
cystitis
Blood in urine (macroscopic
hematuria) fever, dysuria
11, 4, 7,
1, 21
34, 35
Gastro-enteritis Diarrhea especially in children
<4 years old
Low grade fever
40-42,
31, 25-
28,
3, 7, 2, 9,
12, 13, 18

21. LABORASTORY DIAGNOSIS
Methods
Rapid:
Microscopy: electron;
immuno-fluorescent;
Virological:
Isolation of viruses in tissue culture (HeLa, Hep -2, KB);
Indication by CPE, IFT, CFT, ELISA, RIA;
Identification by NT, HIT with monky’s and white rat’s red blood
cells
Serological - is mainly used for epidemiologic studies
Other detection methods in current use include polymerase chain
reaction and nucleic acid probes.

22. Prevention
Handwashing
Contact precautions, respiratory precautions in health care settings
Adequate chlorination of swimming pools
Sterilization / disinfection of ophthalmologic equipment and use of
single dose vials of ophthalmic medications
Vaccine: live, enteric coated, oral vaccine (types 4, 7, 21)
Immunity
The majority of newborn infants possess passive immunity which
they lose at the age of 6 months.
Susceptibility prevails at the age from 6 months to 5 years.
Children older than 5 years of age possess antibodies and rarely
contract adenoviral diseases. A relatively low diseases incidence
among adults is due to immunity acquired following an acute or
asymptomatic form of the disease.
The immunity is type-specific in character.

23. HERPESVIRIDAE FAMILY
Herpes viruses are a leading cause of human viral
disease, second only to influenza and cold viruses.
They are capable of causing overt disease or remaining
silent for many years only to be reactivated, for example
as shingles.
The name herpes comes from the Latin herpes which,
in turn, comes from the Greek word herpein which
means to creep. This reflects the creeping or spreading
nature of the skin lesions caused by many herpes virus
types.

24. Enveloped icosahedral virus
180 - 200nm;
Linear, double-stranded DNA
The space between the
envelope and the capsid is the
tegument. This contains
virally-encoded proteins and
enzymes involved in the
initiation of replication
Capsid contains 162 doughnut
shaped capsomeres.

25. Antigenic structure
The virus contains two
antigens:
the V-antigen, may be
detect in NT
and the S-antigen
(soluble) – may be
detect in CFT, is
allergen

26. There are at least 25 viruses in the family
Herpesviridae (currently divided into three sub-
families).
Eight or more herpes virus types are known to infect
man frequently

27. Subfamily Genera Species pathogenic
for human
Diseases
Alphaherpes
virinae
Simplexvirus HSV 1
HSV 2
Keratoconjunctivitis
Herpes labialis, herpes
genitalis neonatal herpes,
encephalitis
Varicellovirus Varicella-Zoster
virus
Varicella, herpes zoster
ILTV-like virus Infection
laryngotracheitis
virus
Infection laryngotracheitis
Betaherpes
virinae
Cytomegalovirus Cytomegalovirus Cytomegalovirus infection
Roseolovirus Human herpes virus
6A (HHV-6A)
Human herpes virus
6B (HHV-6B)
Human herpes virus
7-HHV-7
Tropism to T-lymphocytes
Exanthema subitum
(roseola infantum)
Exanthema subitum
HERPESVIRIDAE FAMILY VIRUSES
PATHOGENIC FOR HUMAN

28. Gamma-
herpes
virinae
Lymphocrypto
virus
Epstein-Barr virus
(EBV)
Mononucleosis, Burkitt’s
lymphoma, Nasophayngeal
carcinoma, Lymphoma in
immunodeficient persons
Rhadinovirus Kaposi’s sarcoma-
associated herpesvirus
(HHV-8)
Cercopiteci (monkey)
herpes virus type B
Kaposi’s sarcoma
Cause acute respiratory
diseases at human

29. CULTIVATION
1) on the chorioallantoic membrane of the chick embryo
(12-13 days old) on which it forms inflammatory
necrotic foci.
2) on embryonal lung and kidney tissues of human
orrgin and in cultures of НеLа cells, Detroit-6 cells, etc.
2 type of CPE may be observe (at the same time):
(a) – foci of proliferation (which consist of some layers of
oval cell);
(b) – multinuclear syncytium.
3) on laboratory animals. In case of intra cerebrum
inoculation – encephalitis evolves; in case of inoculation
into the cornea - cerato-conjunctivitis will develop.

30. HERPES VIRUS REPLICATION

34. PATHOGENESIS
The virus infects epithelial mucosal cells or lymphocytes.
- then travels up peripheral nerves to a nucleated neurone where it may stay
for years followed by reactivation. A reddened area gives rise to a macula
which crusts to form a papula. The fluid in this blister is full of virus. As long
as the virus is kept moist it can remain infectious.
HSV-1 and HSV-2 first infect cells of the mucoepithelia or enter through
wounds. They then frequently set up latent infections in neuronal cells. The site
of the initial infection depends on the way in which the patient acquires the
virus.
Once epithelial cells are infected, there is replication of the virus around the
lesion and entry into the innervating neurone. The virus travels along the
neurone (by a process called retrograde transport) to the ganglion
(ex.trigeminal or sacral ganglia).

35. The virus can also travel in the opposite direction to arrive
at the mucosa that was initially infected. Vesicles
containing infectious virus are formed on the muscosa
and the virus spreads. The vesicle heals and there is
usually no scar as a result.
Herpes simplex 1 and 2 can infect both humans and other
animals but only humans show symptoms of disease.
Both types of HSV can also persistently infect
macrophages and lymphocytes. The presence of the
virus is often indicated by the formation of syncytia and
inclusion bodies in the nucleus.

36. CLINIC FORMS OF HERPES
INFECTION- Primary and Recurrent
Primary herpes is the result of infection by direct contact or by the
air-droplet route.
herpetic fever or, less frequently, as herpes simplex.
(an increase of temperature to 39-40°С, severe headache, meningeal
symptoms, vomiting, hyperaemia of the conjunctivas, and
inflammation of the lymph nodes. On the following day а
vesicular eruption usually appears on the lips, the temperature
falls, and the disease takes the course of herpes simplex.
Initial infection with herpes simplex type 1 usually occurs in early
childhood. The portal of entry is normally the oral mucosa (“oral
type”) and the infection usually manifests as a gingivostomatitis.
The initial infection with HSV type 2 normally affects the
urogenital area (“genital type”) and can be contracted despite an
existing HSV type 1 infection.
Herpes recurrence is frequently encountered with certain diseases
(malaria, influenza, acute catarrhal conditions, lobar pneumonia,
meningitis, intoxications, psychic disorders), traumas, and

39. VARICELLA-ZOSTER VIRUS (ALSO KNOWN
AS HERPES ZOSTER VIRUS, HUMAN HERPES
VIRUS-3)
Zoster means girdle from the characteristic rash that forms a belt
around the thorax in many patients.
The structure of Varicella virus is very similar to Herpes Simplex
virus although the genome is somewhat smaller
This virus causes two major diseases, chicken-pox (Varicella),
usually in childhood, and shingles, later in life.
Shingles (Zoster) is a reactivation of an earlier varicella infection.

40. CHICKENPOX
The patient is the source of infection.
The causative agent is spread by the air-droplet route.
The patient is infectious from the last days of
incubation and to the time the crusts fall off.
The incubation period lasts from 2 to 3 weeks.
Pathogenesis
The portals of entry are the nasopharyngeal space and
the conjunctiva. From there, the virus undergoes a
viremic phase in which it is transported by the blood to
the skin, where the typical exanthem is produced.
Eruption ceases on the fifth day of the disease.

41. SYMPTOMS OF CHICKEN POX
Rash is pleomorphic, monolocular, appears with
temperature anywhere on the body, but usually first on
the back, than the face, head, mouth, main body and
arms and legs (never on palms and foots).
The lessions appear at different times and within a day or
so go through a characteristic evolution from macule to
papule to vesicle to crusts (without scars).

43. HERPES ZOSTER (SHINGLES)
- is reactivation of varicella.
It can occur at any age, but becomes increasingly common with
advancing age.
It begins with pain in the area supplied by a nerve of sensation,
often on the chest or abdomen, but sometimes on the face, or
arm or leg. After a few days to two weeks the characterisc rash
of varicella appears along the course of the nerve. The rash
subsides within a week, but pain may persist for weeks or
months.

45. Treatment
As with HSV, acyclovir (or other nucleoside analogs) can
be useful, particular in preventing dissemination in
immunosuppressed patients.
Varicella immunoglobulin can also be used. Normally,
however, only supportive care is used in children who
quickly recover if they mount an adequate cell-mediated
response.
Vaccine
There is a live attenuated vaccine virus and this is used in
the United States. It leads to antibody production and cell-
mediated immunity. It can be used post-exposure.

46. LABORATORY DIAGNOSIS
Rapid methods: specimens – smears from mucous membranes, m-l
from vesicles and other rash-elements, biopsy specimens from the
lesions :
- IFT (direct and indirect);
- electronic microscopy;
- studying slides stained by Romanovsky’s or by Morozov’s
technics (to detect intra nuclear inclusions)
2. Virological method: specimens - smears from mucous membranes,
m-l from vesicles and other rash-elements, cerebro-spinal fluid,
blood, scrape from cornea
- obtaining: in tissue culture; on chorion-allantois membrane of
chick embryo; on labоratory animals
- detection: - by CPE; characteristic cytopathic effects (plaque)
including multinucleated cells
- by HAT

47. Herpes simplex 1:
Histological stain. Note the
multinucleate cell with dark
staining inclusions
3. Allergic test – by on cutaneous
test
4. Biological method (look at
virological – cultivation on
lab.animals)
5. Serological method: serum in
serologic tests: NT, CFT, PHAT,
IFT, IHAT.

48. Herpes simplex virus on and in a
peripheral blood lymphocyte
© Dennis Kunkel Microscopy, Inc.
Used with permission
Herpes simplex virus in cellular
vacuoles and cytoplasm of
peripheral blood lymphocyte
© Dennis Kunkel Microscopy, Inc. Used
with permission

49. EPSTEIN- BARR VIRUS
(GAMMAHERPESVIRINAE)
Epstein-Barr virus is the causative agent of Burkitt's
lymphoma in Africa, nasal pharyngeal carcinoma in
the orient and infectious mononucleosis in the west. It
was first discovered as the causative agent of Burkitt's
lymphoma and it was later found that patients with
infectious mononucleosis have antibodies that react
with Burkitt's lymphoma cells.
The virus only infects a small number of cell types that
express the receptor for complement C3d component
(CR2 or CD21). These are certain epithelial cells (oro-
and naso-pharynx) and B lymphocytes. This explains
the cellular tropism of the virus.

50. BURKITT'S LYMPHOMA
This is a tumor of the jaw and face found in children
This lymphoma is endemic in equatorial Africa but only
occurs rarely elsewhere. Why this is so is unclear but
there is probably a genetic reason possibly involving an
association with malaria. Persons who are resistant to
malaria appear to be susceptible to progression to the
lymphoma.

51. Burkitt's lymphoma histological stain.
Notice the large multinucleated cells

52. INFECTIOUS MONONUCLEOSIS
The primary infection is often asymptomatic but the patient may
shed infectious virus for many years. Some patients develop
infectious mononucleosis after 1-2 months of infection. The disease is
characterized by malaise, lymphadenopathy, tonsillitis, enlarged
spleen and liver and fever. The fever may persist for more than a
week. There may also be a rash. The severity of disease often
depends on age (with younger patients resolving the disease more
quickly) and resolution usually occurs in 1 to 4 weeks.
Complications: meningitis, encephalitis, myelitis. Secondary
infections, autoimmune hemolytic anemia, thrombocytopenia,
agranulocytosis, aplastic anemia may also occur.
As noted above a chronic syndrome may also occur. The
symptoms are similar to those reported for chronic fatigue
syndrome (headaches, sore throat and low fever) but EBV is
probably not the cause of chronic fatigue syndrome.

53. Diagnosis
In infectious mononucleosis, blood smears show the atypical
lymphocytes (Downey cells). There are also serological tests
available. Heterophile antibodies are produced by the proliferating
B cells and these include an IgM that interacts with Paul-Bunnell
antigen on sheep red blood cells.
Leukemia cells that
contain Epstein Barr
virus using a FA
staining

54. CYTOMEGALOVIRUS
Cytomegalovirus has the largest genome of all herpes viruses and
appears only to replicate in human cells. Its name derives form the
fact that, like other herpes viruses, it can form multinucleated cells
(syncytia) with characteristically staining inclusions. Some cells
such as macrophages and fibroblasts support a productive
infection while a latent infection is set up in several cell types
including T lymphocytes and stromal cells of the bone marrow.
There is only one serotype.

55. PATHOGENESIS
Cytomegalovirus causes no symptoms in children and at most
mild disease in adults.
The virus first infects the upper respiratory tract and then local
lymphocytes. Circulating lymphocytes then spread the virus to
other lymphocytes and monocytes in spleen and lymph nodes.
The virus finally spreads to a variety of epithelial cells including
those of salivary glands, kidney tubules, testes, epididymis and
cervix.
Infection is usually asymptomatic (sub-clinical) but glandular
fever is sometimes seen in young adults.
The virus can inhibit T cell responses. The virus elicits both
humoral antibodies and cell-mediated immunity but the infection
is not cleared. Cell-mediated immunity, not humoral antibodies,
controls the infection

56. Congenital disease
There are two instances in which cytomegalovirus can cause
serious disease. During a primary infection of the mother, the
virus can spread via the placenta to the fetus and congenital
abnormalities can occur; in fact, this virus is the most common
viral cause of congenital disease. Up to one in forty newborns in
the United States are infected by the virus. Abnormalities include
microcephaly, rash, brain calcification and hepatosplenomegaly.
These may result in hearing loss (bilateral or unilateral) and
retardation. As might be expected, when reactivation occurs in a
pregnant mother (usually reactivation in the cervix), the
symptoms are less severe because of the mothers seropositivity. In
this case, congenital abnormalities are rare.
Besides infection in utero, infants may be infected perinatally

57. Diagnosis
Most infections are asymptomatic and therefore go undiagnosed.
There are fluorescent antibody and ELIZA tests. Multinucleated
(cytomegalinic) cells with characteristic inclusions can be seen in
biopsies of many tissues.
Treatment
Ganciclovir, which inhibits the replication of all human herpes
viruses, is usually used, especially to treat retinitis. Foscarnet is also
approved in the US. Acyclovir is not effective.
A vaccine is being developed but the best way to avoid the virus is to
restrict contact between infected children and pregnant women.
Also since cytomegalovirus is sexually transmitted, condoms can limit
spread.

58. H&E stain of lung section showing nuclear
inclusions with the appearance of an "owl's
eye". The inclusion is surrounded by a clear
halo that extends to the nuclear membrane.
CMV infection can occur without the typical
cytomegalic cells.
H&E stain of CMV-infected cells in
lung of AIDS patient. Nuclear
inclusions can be seen

59. Specimen of human embryonic lung reveals the presence of
cytomegalovirus using immunofluorescent technique. Mag.
25X. CDC/Dr. Craig Lyerla

60. POXVIRUSES

61. POXVIRUSES
There are several reasons why poxviruses are of
importance:
Certain poxviruses are of historic note, such as
smallpox and vaccinia (cow pox, which was used
in the smallpox vaccine
Pox viruses may be possible agents of
bioterrorism
Pox viruses are used in new techniques of
vaccine development (such as genetically-
engineered vaccinia)
Some members of this family infect man
(molluscum contagium , monkey pox, cow pox).
Note: chicken pox is caused by a herpes virus
which is not a member of the poxviridae

62. Possible scheme for
the formation of
infectious pox
virions. The virus
core becomes
wrapped in
cytoplasmic
membrane and may
escape when the
host cell is lyzed.
Some other
membrane-bound
virions may bud
through other
membranes, in
which case they
have two
membranes. In
either case, the
virions are
infectious. Adapted
from Baron, S. Ed.
Medical Microbiology
4th Edition. 1996.