(CHICKEN POX)

• An acute, highly

contagious exanthem.

• Most often occurs in

childhood.

• Result of primary infection

of a susceptible individual.

EPIDEMIOLOGY

1.Worldwide in distribution,

whereas the proportion of

susceptible adults is even

higher in Asia, Africa, and

the Middle East.

2.No difference in racial or

sexual susceptibility.

3.Humans are the only

known reservoir.

4.Vectors play no role in

transmission.

5.The mean incubation

period is 14 or 15 days,

with a rarge of 10 to 23

days.

6.The major route by which

varicella is acquired and

transmitted is thought to

be the respiratory tract

7.Airborne droplets

constitute an important

mechanism of transmission,

but can also be spread by

direct contact

ETIOLOGY

1.VZV is a member of the

herpes virus family.

2.There is only one VZV

serotype.

3.A number of antigens are

present in the virion and

produced infected cells.

4.Studies of molecular

biology and its

pathogenesis have been

hampered.

PATHOGENESIS

1.Entry of the virus is

through the mucosa of

the upper respiratory

tract and oropharynx.

2.Initial multiplication at this portal dissemination small amounts of virus blood and lymphatics (primary viremia) by cells of RES.

3.Incubating infection is partially contaired by innate host defenses and by developing immune responses.

4.Virus replication eventually overwhelms these still undeveloped defenses secondary viremia occurs (zweeks often infection) fever and malaise and disseminates throughout the body especially skin and mucous membranes.

5.Cyclic viremia is terminate after about 3 days.

6.Host immune responses terminate viremia and limit the progression of varicella lesions.

7.IgG, IgM, and IgA of VZV are detectable 2 to 5 days after onset of clinical varicella.

8.Reach maximum titers during second or third week decline slowly persist in low levels for life

9.Cell mediated immunity is more important than humoral immunity in recovery from varicella.

CLINICAL MANIFESTATIONS

Prodrome of Varicella1.Uncommon in young

children.2.In older children and

adults, rash preceded by 2 to 3 day of fever , chills, malaise, headache, anorexia, severe backache.

Rash of Varicella1.Benigns on the face and

scalp.2.Spreads rapidy to the

trunk, with relative sparing of the extremities.

3.Central in distribution.4.More profuse in lows and

protected parts of the body.

5.Rose colored macules papule vesicles pustules crusts.

6.Vesicle is superficial and thin walled like a drop of water

7.Vesicle can also develop in the mucous membranes

8.Fever that persist is proportional to the severity of rash.

COMPLICATIONS OF VARICELLA

1.Secondary bacterial

infection of skin lesion

(children).

2.Primary varicella

pneumonia (adult).

3.Congenital VZV infection :

asymptomatic infection

severe congenital

malformation.

4.Morbidity and mortality

are markedly increased in

immuno compromised

patients.

5.CNS complication :• Reye’s syndrome.• Acute cerebellar atoxia.• Encephalitis or

meningoencephalitis.• Acute ascending or

transverse myelitis.• Guillain-barre

syndrome.6.Mild hepatitis.

PATHOLOGY

1.Histologically, can’t be

distinguished from herpes

zoster.

2.Ballooning degeneration

(characteristic changes).

CLINICAL DIAGNOSIS

1.The development papulo

vesikular eruption after a

brief and mild (or absent)

prodrome symptoms.

Characteristic diagnostic include:

2.Appearance of lesions in

crops with central

distribution.

3.Rapid evolution of lesions.

4.Presence of lesions in all

stages of development in

any area throughout the

acute disease.

5.Presence of lesions in

the mucous membranes

of the mouth.

LABORATORY DIAGNOSIS

1.Routine blood test are

not helpful.

2.Asymptomatic elevation

in ALT and AST.

3.Punch biopsies more

rediable for histologig

examinations.

4.Defenitive diagnosis from

isolation of virus in cell

cultures.

5.Serologic tests.

TREATMENT

Antiviral agents :

• Acyclovir.

• Famciclovir.

• Laciclovir.

• Vidarabine.

• Foscarnet.

TREATMENT OF VARICELLA

1.Generally benign and self-limited.

2.Locally :• Cool compresses.• Calamine lotion.

Orally :• Antihistamines.• Antipyretics.• Antiviral agents.

PREVENTION & CONTROL

1.Passive

immunization.

2.Chemoprophylactic.