2. Chicken pox.
• Varicella-zoster virus (VZV) causes primary,
latent, and recurrent infections.
• The primary infection is manifested as
varicella (chickenpox) and results in
establishment of a life long latent infection of
sensory ganglion neurons.
4/4/2024 Dr muhumed 2
3. Cont...
• Reactivation of the latent infection causes
herpes zoster (shingles).
• Morbidity and mortality are higher in
immunocompetent infants, adolescents, and
adults as well as in immunocompromised
persons.
• predisposes to severe group A Streptococcus
and Staphylococcus aureus infections.
4/4/2024 Dr muhumed 3
4. Cont...
• Varicella and herpes zoster can be
treated with antiviral drugs.
• Primary clinical disease can be
prevented by immunization with live-
attenuated VZV vaccine (varicella
vaccine).
4/4/2024 Dr muhumed 4
5. PATHOGENESIS
• VZV is transmitted by contact with oropharyngeal
secretions and the fluid of skin lesions of infected
individuals, either by airborne spread or through
direct contact.
• Primary infection (varicella) results from
inoculation of the virus onto the mucosa of the
upper respiratory tract and tonsillar lymphoid
tissue.
4/4/2024 Dr muhumed 5
6. Cont..
• During the early part of the 10-21 day
incubation period, virus replicates in the
local lymphoid tissue, and then a brief
subclinical viremia spreads the virus to
the reticuloendothelial system.
4/4/2024 Dr muhumed 6
7. Clinical features of VZV.
• Varicella lesions often appear first on the scalp,
face, or trunk.
• The initial exanthem consists of intensely pruritic
erythematous macules that evolve through the
papular stage to form clear, fluid-filled vesicles.
• Clouding and umbilication of the lesions begin in
24-48 hr.
4/4/2024 Dr muhumed 7
8. Cont...
• While the initial lesions are crusting, new
crops form on the trunk and then the
extremities , the simultaneous presence
of lesions in various stages of evolution
is characteristic of varicella .
4/4/2024 Dr muhumed 8
9. Cont..
• The best known symptom of chickenpox is the
itchy, red rash that breaks out on the face, scalp,
chest, back, and sometimes arms and legs.
• The rash usually appears about 2 weeks after
exposure to the virus and begins as superficial
spots.
4/4/2024 Dr muhumed 9
10. Cont...
• The spots quickly fill with a clear fluid,
rupture, and turn crusty.
• The scabs then fall off in a week or two
weeks.
• The rash continues to break out for the
first 1 to 5 days, so spots at various
stages of development may be present
at the same time.
4/4/2024 Dr muhumed 10
11. Cont...
• Chickenpox seldom lasts for more than 2
weeks, from the appearance of the first
rash to the disappearance of the last
one.
• secondary infection of the ruptured rash
by bacteria may cause high fever and
skin scarring.
4/4/2024 Dr muhumed 11
15. Complications.
1.Bacterial Infections
• Secondary bacterial infections of the
skin, usually caused by group A
Streptococcus and S. aureus, may occur
in up to 5% of children with varicella.
• These range from impetigo to cellulitis,
lymphadenitis, and subcutaneous
abscesses.
4/4/2024 Dr muhumed 15
16. Cont...
2.Encephalitis and Cerebellar Ataxia.
• Encephalitis (1 per 50,000 cases of varicella
in unvaccinated children) and acute
cerebellar ataxia (1 per 4,000 cases of
varicella in unvaccinated children) are well-
described neurologic complications of
varicella.
4/4/2024 Dr muhumed 16
17. Cont...
• morbidity from central nervous system
complications is highest among patients
younger than 5 yr and older than 20 yr.
• Nuchal rigidity, altered consciousness,
and seizures characterize
meningoencephalitis.
4/4/2024 Dr muhumed 17
18. 3.Pneumonia
• Respiratory symptoms, which may include
cough, dyspnoea, cyanosis, pleuritic chest
pain, and haemoptysis, usually begin within 1-
6 days after the onset of the rash.
• Smoking has been described as a risk factor
for severe pneumonia complicating varicella.
4/4/2024 Dr muhumed 18
19. 4.Herpes Zoster
• Herpes zoster manifests as vesicular lesions
clustered within 1 or, less commonly, 2 adjacent
dermatomes In the elderly, herpes zoster typically
begins with burning pain followed by clusters of
skin lesions in a dermatomal pattern.
4/4/2024 Dr muhumed 19
20. Cont...
• the most frequent complication is post
herpetic neuralgia, a painful condition
that affects the nerves despite
resolution of the skin lesions.
4/4/2024 Dr muhumed 20
22. Treatment.
• The only antiviral drug available in liquid
formulation that is licensed for
treatment of varicella for paediatric use
is acyclovir.
• Oral therapy with acyclovir (20
mg/kg/dose,maximum: 800 mg/dose)
given as 4 doses/day for 5 days.
4/4/2024 Dr muhumed 22
23. Cont...
• Some experts recommend the use of
famciclovir or valacyclovir in older
children who can swallow tablets.
• These drugs are highly active against VZV
by the same mechanism as acyclovir and
are better absorbed by the oral route
than acyclovir.
4/4/2024 Dr muhumed 23
24. Cont...
• Intravenous therapy is indicated for severe disease
and for varicella in immuno compromised patients.
• Any patient who has signs of disseminated VZV,
including pneumonia, severe hepatitis,
thrombocytopenia, or encephalitis, should receive
immediate treatment.
4/4/2024 Dr muhumed 24
25. Cont...
• Acyclovir-resistant VZV has been
identified primarily in children infected
with HIV.
• These children may be treated with
intravenous foscarnet (120 mg/kg/day
divided every 8 hr for up to 3 wks).
4/4/2024 Dr muhumed 25
26. Herpes Zoster
• Antiviral drugs are effective for treatment of
herpes zoster.In healthy adults, acyclovir (800
mg 5 times a day PO for 5-7 days), famciclovir
(500 mg tid PO for 7 days), and valacyclovir
(1,000 mg tid PO for 7 days) reduce the
duration of the illness and the risk for
development of post herpetic neuralgia.
4/4/2024 Dr muhumed 26
27. PREVENTION
• VZV transmission is difficult to prevent,
especially from persons with varicella,
because a person with varicella is
contagious for 24-48 hr before the rash
is apparent.
4/4/2024 Dr muhumed 27
28. Vaccine
• Varicella is a vaccine-preventable
disease.
• Varicella vaccine contains live,
attenuated VZV (Oka strain) and is
indicated for subcutaneous
administration.
4/4/2024 Dr muhumed 28
