2. Viruses are strictly intracellular parasites,
relying on the host cell for their replication.
Herpes viruses, which are large-enveloped,
double-stranded DNA viruses. are one of the
most common human infectious agents,
responsible for a wide spectrum of acute
and chronic diseases.
3. The major members of the group are :
Herpes simplex viruses (HSV-1 and HSV-2)
Varicella-zoster virus
Cytomegalovirus (CMV)
Epstein-Barr virus.
4. HSV has 2 antigenic types, each with
numerous antigenic strains.
Each type has different epidemiologic
patterns of infection.
Many people with HSV antibodies are
asymptomatic.
5. The virus can spread within nerves and cause
a latent infection of sensory and autonomic
ganglia.
Serologic testing and viral culture can assist
in the diagnosis of difficult cases, particularly
CNS infections.
6. Herpes simplex type 1 is associated with
mucocutaneous superficial infections of the
pharynx, skin, oral cavity, vagina, eye, and
brain.
Ophthalmic infection most often manifests
as corneal dendritic or stromal disease, but
may present as acute retinal necrosis.
7. Herpes simplex type 2 is an important sexually
transmitted disease that is associated with
genital infections, aseptic meningitis, and
congenital infection.
The drug of choice for treating acute
systemic infections is acyclovir.
Localized disease can be treated with oral
acyclovir.
8. Topical treatment of skin or mucocutaneous
lesions with acyclovir ointment decreases the
healing time
Two newer antiviral agents, famciclovir and
valacyclovir, are approved for the treatment
of herpes zoster and herpes simplex.
HSV is also sensitive to vidarabine.
9. Varicella-zoster virus (VZV), also sometimes
referred to as herpes zoster, produces infection
in a manner similar to herpes simplex
Primary infection usually occurs in childhood in the
form of chickenpox (varicella), a generalized
vesicular rash accompanied by mild constitutional
symptoms.
10. Other neurological syndromes following
herpes zoster involvement include segmental
myelitis,Guillain-Barre syndrome etc..
The incidence of herpes zoster is 2 to 3 times
higher in patients older than age 60.
11. Treatment of acute infection in
immunocompromised patients or those with
visceral involvement may include acyclovir,
famciclovir, or valacyclovir.
Newer drugs being evaluated for resistant
VZV strains or concomitant HIV infection
include sorivudine, brivudine, netivudine,
lobucavir, foscarnet, and cidofovir.
12. A live attenuated varicella vaccine (Varivax) is
available for prevention of primary disease,
and it appears to also reduce the incidence of
recurrentVZV infection and neuralgia.
This vaccine is recommended for children,
patients with chronic diseases or leukemia,
and patients receiving immunosuppressive
therapy.
13. Cytomegalovirus is a ubiquitous human virus.
Serologic testing is done to diagnosis CMV
infection.
14. Clinical syndromes with greatest morbidity
include congenitalCMV disease, with a
20% incidence of hearing loss or mental
retardation and a 0.1% incidence of various
other congenital disorders, including
jaundice, hepatosplenomegaly, anemia,
microcephaly, and chorioretinitis.
15. In immunocompromised patients, CMV
interstitial pneumonia carries a 90% mortality
rate.
Disseminated spread to the gastrointestinal
tract, CNS, and eye is common in patients with
AIDS.
16. CMV retinitis and colitis have been
successfully treated with the nucleoside
derivative ganciclovir, which is available for
intravenous, oral, or intravitreal routes
Intraocular ganciclovir insert is also available
for the treatment of retinitis.
17. Intravenous foscarnet and cidofovir have also
been effective in the treatment of retinitis.
Intravitreal cidofovir given at 6-week intervals
was highly effective for treating retinitis.
Valganciclovir is a well-tolerated, newer oral
agent that is highly effective in the treatment
of CMV infection, including retinitis.
18. Childhood infections are usually asymptomatic,
with symptomatic disease occurring in young
adults
Infectious mononucleosis is the usual clinical
disease in most symptomatic adults.
EBV is epidemiologically associated with Burkitt
lymphoma and nasopharyngeal carcinoma.
19. Treatment of acute disease is largely
supportive - acyclovir and ganciclovir, which
decrease viral replication in tissue culture.
No vaccine is currently available against EBV,
but research is ongoing toward developing a
cytotoxicT-cell-based vaccine.
