2. INTRODUCTION
EPIDEMIOLOGY AND TRANSMISSION
STRUCTURE
REPLICATION
PATHOGENESIS AND CLINICAL SIGNIFICANCE
LABORATORY DIAGNOSIS
TREATMENT AND PREVENTION
3. Herpes (Greek: creep or crawl)
Herpes simplex viruses belong to the ubiquitous
Herpesviridae family
Human herpes simplex virus (HSV) causes contagious
infection with a large reservoir in the general
population
Herpesviruses are able to establish lifelong persistent
infections in their hosts and undergo periodic
reactivation ; incurable
HSV has a potential for significant complications in the
immunocompromised host
4. HSV-1 is normally associated with orofacial
infections and encephalitis
HSV-2 usually causes genital infections and can be
transmitted from infected mothers to neonates
Both viruses establish latent infections in sensory
neurons and, upon reactivation, cause lesions at or
near point of entry into the body
5. Biologic properties Examples
Subfamily(
“herpesviri
nae)
Growth cycle and
cytopathology
Latent
infections
Genus
(“virus)
Official name
(“Human
herpesvirus”)
Common name
Alpha Short, cytolytic Neurons Simplex 1 Herpes simplex virus type
1
2 Herpes simplex virus type
2
Varicello 3 Varicella-zoster virus
Beta Long, cytomegalic Glands,
kidneys
Cytomegalo 5 Cytomegalovirus
Long,
lymphoproliferative
Lymphoid
tissue
Roselo 6 Human herpesvirus 6
7 Human herpesvirus 7
Gamma Variable,
lymphoproliferative
Lymphoid
tissue
Lymphocrypto 4 Epstein-Barr virus
Rhadino 8 Kaposi's sarcoma-
associated herpesvirus
6. HSV-associated diseases are among
the most wide-spread infections
affecting nearly 60-95% of human
adults
No animal reservoirs or vectors
Highest incidence of HSV-1 infection
occurs among children 6 months to 3
years of age
70–90% of persons thus acquire type 1
antibodies by adulthood
Primary infection by HSV-2 is more
common in young adults
7. Transmission of both HSV types is by
direct contact with virus-containing
secretions or with lesions on mucosal
or cutaneous surfaces
HSV-1 is spread by contact, usually by infected saliva
HSV-1 primarily infects skin above the waist
HSV-2 is transmitted sexually or from a maternal genital
infection to a newborn
HSV-2 primarily infects skin below the waist
8. Virions are spherical, 150-200nm in
diameter
HSV-1 and HSV-2 contains
i. an envelope- derived from the
nuclear membrane of the
infected cell; contains viral
glycoproteins
ii. a tegument—an amorphous layer
of proteins that surround the capsid
iii. an icosahedral capsid
iv. Genome (linear, a large
double-stranded viral DNA; encoding
70-200 proteins)
9. i. Virus adsorption and penetration
ii. Viral DNA replication and
nucleocapsid assembly
iii. Acquisition of the viral envelope
iv. Latency
10. HSV causes cytolytic
infections
Pathologic changes are due to
necrosis of infected cells
together with the inflammatory
response
Viral cytopathy
11. Ballooning of infected cells
Production of Cowdry type
A intranuclear (Lipschutz)
inclusion bodies
Margination of chromatin
Formation of
multinucleated giant cells
16. Reactivation
Hormonal changes, fever, and physical damage
Severity of any systemic symptoms is considerably
less than that of a primary infection
Many recurrences are characterized by shedding of
infectious virus in the absence of visible lesions
HSV-1:
Reactivation frequency- none to several a year
Herpes labialis or cold sores, fever blisters
HSV-2:
Reactivation frequency- monthly
Asymptomatic; viral shedding
17. A. Cytopathology:
A rapid cytologic method
Scrapings obtained from the base
of a vesicle is stained with 1% aq.
solution of toluidine blue ‘0’ for
15 seconds
Presence of multinucleated giant
cells or ‘Tzanck cells’ = + HSV
Intranuclear inclusion bodies with
Giemsa-stained smears
18. B. Isolation and identification:
Inoculation of tissue cultures in human diploid
fibroblasts is preferred for viral isolation
Typical cytopathic changes may be seen in 24-48 hrs
C. Polymerase chain reaction:
D. Serology:
Antibodies appear in 4–7 days after infection; reach a
peak in 2–4 weeks
Rise in Ab titre may be demonstrated by ELISA or
complement fixation tests
19. Aciclovir, Valaciclovir, Famciclovir
Asymptomatic shedding is
frequent in patients with genital
herpes
Transmission can be reduced
by:
avoidance of contact with
potential virus-shedding lesions
safe sexual practice
antiviral therapy
20. Harvey RA, Champe PC, Fischer BD. Lippincott’s
Illustrated Reviews: Microbiology. 2nd edition.
2007.
Jawetz, Melnick & Adelberg. Medical
Microbiology. The McGraw-Hill Companies. 25th
edition
Richard J Whitley, Bernard Roizman. Herpes
simplex virus infections. Lancet. 2001; 357: 1513–
18
Fatahzadeh M & Schwartz RA. Human herpes
simplex virus infections: Epidemiology,
pathogenesis, symptomatology, diagnosis and
management. JAM ACAD DERMATOL. 2007;
737-763