This document summarizes key information about DNA viruses, including poxviruses, herpesviruses, and cytomegalovirus. It describes the morphology and cultivation of poxviruses, as well as viruses that cause human infections like smallpox, vaccinia, and molluscum contagiosum. Herpes simplex virus types 1 and 2 are discussed, along with the infections they cause. Varicella-zoster virus is covered, explaining chickenpox and shingles. Cytomegalovirus transmission, pathogenesis, and laboratory diagnosis are also summarized.

1. DNA VIRUSES
By chinju jose
Lecturer

2. I. POXVIRUSES
• Pox viruses belong to the family Poxviridae and
cause a number of human diseases.
Morphology
The Poxviruses are brick-shaped. They are the
largest animal viruses measuring 300 x 200 x 100
nm in size and can be seen under the light
microscope.

3. • . Cultivation
They grow in chorioallantoic membrane (CAM) of
chick embryo and in tissue culture. Tissue
cultures of monkey kidney and chick embryo
cells can be used to grow these viruses.

4. Viruses Causing Human Infections
• 1. Variola
• Variola virus causes smallpox.Smallpox has been
eradicated and routine vaccination is now
stopped. On May 8, 1980, the WHO announced
the global eradication of small pox.

5. • 2. Vaccinia
Origin of vaccinia virus is not known. It may have
evolved from cowpox or smallpox virus. It is an
'artificial virus' and does not occur in nature as such.
3. Molluscum Contagiosum
It is a benign epidermal tumour-like lesion, that
occurs only in humans. It is a contagious disease.
The virus is also transmitted sexually in adults

6. • Prophylaxis
A natural infection of smallpox gives complete
protection against reinfection. a Vaccination
with vaccinia induces protection against
smallpox for about five years.

7. HERPESVIRUSES
• Herpesviruses are included in the family Herpesviridae.
A HERPES SIMPLEX VIRUS (HSV)
Man is the only natural host. There are two types of the
herpes simplex virus, type 1 and type 2.
Herpes simples type 1 is usually associated with oral and
ocular lesions.
type 2 is responsible for the majority of genital infections.

8. HERPESVIRUSES

9. Infections HSV-1:
• 1. acute gingivostomatitis
• 2. herpes labialis
• 3. keratoconjunctivitis
• 4. eczema herpeticum
• 5. encephalitis
• 6. dendritic keratitis

10. Infections HSV-1:
acute gingivostomatitis herpes labialis

11. keratoconjunctivitis eczema herpeticum

12. dendritic keratitis encephalitis

13. HSV-2:
1 genital herpes (penis, urethra, cervix, vulva,
vagina)
2 neonatal herpes
3 aseptic meningitis

14. HSV-2
genital herpes neonatal herpes

15. aseptic meningitis

16. LABORATORY DIAGNOSIS
1. Specimens
Specimens include
vesicle fluid
skin swab
saliva
corneal scrapings
 brain biopsy
 CSF
according to the site of involvement.

17. • 2. Direct ExaminationSmears prepared from
scrapings from the base of vesicles are stained with
toludine blue. Multinucleated giant cells (Tzanck
cells), are present in a positive smear.
• Herpes virions may be demonstrated in specimens by
electron microscopy. Viral antigens can also be
demonstrated in the scrapings from the base of the
lesions and tissue preparations, stained by immuno
fluorescent staining.

18. toludine blue

19. 3. Tissue Culture
Virus can be isolated on human fibroblasts, HEp-2
cells, Vero cells and chorioallantoic membrane.
4. Polymerase Chain Reaction (PCR)
PCR can be used for detection of HSV DNA in CSF.
C. Chemotherapy
HSV infection can be treated with acyclovir. It may be
used in the form of ointment for the treatment of
ocular lesions.

20. • VARICELLA-ZOSTER
Varicella (chickenpox) and herpes zoster (shingles)
are caused by a single virus, for which it is named
Varicella-zoster virus (VZV). Chickenpox
follows primary infection in a non-immune
individual, whereas herpes zoster is a reactivation
of the latent virus when immunity falls to
ineffective level. VZV is similar to the herpes
simplex virus in its morphology.

21. VARICELLA-ZOSTER

22. • VaricellaChickenpox is one of the commonest
childhood exanthemata. The virus enters e
through respiratory route. The source of
infection is a chickenpox or herpes-zoster
patient. It is a highly infectious disease
characterised by vesicular rash mostly on the
trunk. The rash progresses through macule,
papule, vesicle, pustule and scab.

23. VaricellaChickenpox

24. HERPES ZOSTER
• While chickenpox is typically a disease of childhood,
herpes zoster is a disease of old age and occurs usually
in persons who had chickenpox several years earlier.
The virus remains latent in the sensory ganglia. Years
after the initial infection, when the immunity has fallen
to ineffective levels, the virus may be reactivated. The
reactivation is associated with the inflammation of the
nerve which leads to neuritic pain that often precedes
the skin lesions.

25. HERPES ZOSTER

26. IMMUNITY
Although the single virus is responsible for both
the conditions, one attack of chickenpox
confers life long immunity, but antibody fails
to eliminate the virus from dorsal root ganglia.
Hence, zoster occurs in persons.

27. Laboratory Diagnosis
Diagnosis is usually clinical.
• Laboratory diagnosis includes
1. Direct Microscopy Stained smears from the base of
early vesicles show multinucleated giant cells and type
A intranuclear inclusions bodies under light
microscope. Herpes particles can also be detected by
electron microscopy. Flourescent antibody technique
using monoclonal antibody is another rapid method for
diagnosis.

28. 2. Virus Isolation
Virus can be isolated in human fibroblast cells,
human amnion.
3. Serology Varicella-
zoster specific IgM antibody in patient's serum can
be detected by ELISA.
Treatment
Acyclovir is effective in the treatment of severe
varicella and zoster.

29. CYTOMEGALOVIRUS
• Cytomegalovirus infections are almost always
in apparent, leading to prolonged latency, with
occasional reactivation. An individual infected
with CMV carries the virus for life. The virus
is shed in urine saliva, semen, cervical
secretions, tears and breast milk.

30. CYTOMEGALOVIRUS

31. PATHOGENESIS
• Cytomegalovirus can be transmitted
transplacentally from a mother with latent
infection to the foetus. Congenital infection
may remain inapparent (asymptomatic) at birth
or may lead to cytomegalic inclusion disease
which is often fatal.

32. • Postnatal infections are usually inapparent. This
may be acquired by sexual intercourse, blood
transfusion and organ transplantation. Clinical
disease in adults resembles infectious
mononucleosis. CMV may cause disseminated
infection in immuno compromised individuals
and can even lead to fatal infections. CMV is an
important pathogen in AIDS.

33. Laboratory Diagnosis1
1) Specimens
CMV can be isolated from urine, saliva, breast milk,
semen, cervical secretions and blood leucocytes
1) Demonstration of Cytomegalic Cells
Enlarged cells with large intranuclear "owl's eye"
appearance inclusions (cytomegalic cells) can be
demonstrated in the centrifuged deposits from urine or
saliva. It is a simpler but less reliable technique.

34. 3. Isolation of Virus
Virus can be grown in human fibroblast cultures.
4. Serology
CMV-specific IgM can be detected in the serum
by ELISA.
TREATMENT
Ganciclovir is the drug of choise