CHICKEN POX

Dr. sukhwant singh

* Chicken Pox is an acute, extremely contagious infection caused by -“Varicella Zoster Virus” ( VZV ) * It is a benign illness of childhood characterized by exanthematous vesicular rash.

HOST FACTORS

* Occurs Primarily among children under 10 years.

* Both sexes & all races infected equally often.

* More severe in adults.

* One attack gives durable immunity.

: ENVIRONMENT :

(Shows seasonal trend)

* First six months of the year in

tropical regions.* Late winter and early spring

in temperate regions.

* Over crowding favours its transmission.

AGENT

* Varicella Zoster Virus. (Human alpha herpes virus-3). * Member of Herpesviridae. * Double stranded DNA. * Size 150 – 200 nm. * Molecular Weight -80Million. * Only one serotype is known. * Humans are the only hosts of the virus. * Virus can be grown in tissue culture.

SOURCE OF INFECTION

* A Case of Chicken Pox: Virus occurs in the oro- pharyngeal secretions and lesions of skin and mucosa.* Subclinical infections are rare ( Less than 5 % )

TRANSMISSION

* Person to person through droplet nuclei / direct contact ( in case of Herpes Zoster )

* Portal of entry of virus is respiratory tract.

INCUBATION PERIOD

Ranges between 10-21 days

but usually between14-17 days

INFECTIVITY

* Ranges from 1-2 days before the appearance of rash, and 4-

5 days thereafter or until all vesicles are crusted.

* Virus remains latent in the cranial nerves sensory ganglia

& Spinal dorsal root ganglia until reactivated

Clinical Features

PRE-ERUPTIVE STAGE

* Moderate Fever* Backache* Shivering* Malaise

(Lasting about 24 hrs)

In adults, the prodromal illness is more severe and lasts longer

ERUPTIVE STAGE “Rash” comes on the day the fever starts.

* Symmetrical & Centrifugal.* Pleomorphic.* Looks like ‘dew drops’ * Surrounded by an area of inflammation.* Mucosa is generally involved but palms & soles not usually affected.* Vesicles involve corium & dermis

SECONDARY ATTACK RATE

70-90 percent

in susceptible siblings within a household

IMMUNITY

* Maternal antibody protects the infant during first few months of life.* Presence of IgG antibodies correlates with protection against varicella* Cell mediated immunity is important in recovery from V-Z infections

* Natural infection confers lifelong immunity. * However, the virus can remain latent in sensory root Ganglia. *Reduction in cell mediated immunity can result in reactivation of the virus which causes Herpes zoster in 10-30 percent cases. * The disease occurs with greater severity among adults, newborn infants, immunocompromised children and pregnant women.

COMPLICATIONS

* Bacterial super infection of the skin ( Most Common ) Strep. Pyogenes/Staph. Aureus

* C.N.S. involvement in children.

* Varicella pneumonia, Occurs in 20 % cases. ( Most serious complication )

More common in adults than children

: Other Complications :

* Acute cerebellar ataxia* Encephalitis* Varicella hemorrhagical* Corneal lesions* Myocarditis* Reye’s syndrome* Arthritis* Ac. Glomerulo nephritis

Mortality is less than 1% in uncomplicated cases.

PREGNANCY

* Associated with high peri natal mortality, when maternal disease develops within 5 days before delivery or 48 hours thereafter.( Neonatal varicella )

* Mortality rate has been as high as 30 percent in this group. Limb hypoplasia, Cicatricial skin lesions, Microcephaly, low birth weight, cataract, chorioretinitis, deafness, cerebrocortical atrophy & fetal death.

* Maternal infection in first trimester can give rise to

“congenital varicella syndrome”

: LABORATORY DIAGNOSIS :

1. Examination of vesicle fluid under electron microscope ( shows round particles )

2. Scrapings of the floor of the vesicles colored by Giemsa. ( Tzanck smear ) ( shows multinucleated giant cells )

3. Four fold rise in antibody titre.4. Detection of viral DNA by PCR5. Fluorescent Antibody to Membrane Antigen.6. ELISA.

:CONTROL:*Good hygiene – Daily bathing and soaks.* Avoid secondary bacterial infection of the skin by – Meticulous skin care Close cropping of fingernails* Relief of itching – Tepid water bath & wet compresses Topical dressings Antipruritic drugs

Contd… * Disinfection of articles soiled by nose and throat discharges. * Notification of the cases.* Isolation for 6 days after onset of rash.* Drugs – . Acyclovir (800 mg 5 times a day x 5-7 days)

. Famicyclovir (250 mg tid x 5-7 days)

. Valacyclovir ( 1 gm tid x 5-7 days)

PREVENTION

1. VZIG varicella zoster immunoglobulin

Given within 72 hrs of exposure. (12.5 U/Kg, repeated after 3 wks) to exposed susceptible individuals- . Persons with congenital cellular immunodeficiency . HIV/AIDS . Pregnant women . Newborns/Premature infants

2. VACCINE (Live attenuated varicella virus vaccine)

* Recommended for 12-18 months children who have not had Chicken pox.

* Persons above 12 years need 2 doses 4-8 wks apart.

* Duration of immunity is probably 10 years.

* The vaccine is 90%effective in preventing varicella in an outbreak, when given within 3-5 days after exposure.

* Sero conversion occurs in 95% children after single dose.

* In adolescents and adults, sero conversion occurs in 78 % after one dose and 99 % after two doses

ADVERSE REACTIONS OF VACCINE

* Tenderness & erythema at injection site (25 % )

* Fever ( 10-15% )

* Localized maculopapular rash ( 5% )

CONTRAINDICATIONS TO VACCINE

* Pregnancy

* Immunodeficiency

* Allergy to Neomycin

* Salicylates should be avoided for 6 weeks following vaccination