Chickenpox is caused by the varicella zoster virus. It presents as an itchy rash that starts on the torso and spreads outward. It is highly contagious but usually mild in children. Complications can include bacterial skin infections or pneumonia. Vaccination provides effective protection against chickenpox.
2. * 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.
3. 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.
4. : 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.
5. 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.
6. 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 % )
7. TRANSMISSION* Person to person through droplet nuclei / direct contact ( in case of Herpes Zoster )* Portal of entry of virus is respiratory tract.
9. 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
10. Clinical Features
11. PRE-ERUPTIVE STAGE * Moderate Fever* Backache* Shivering* Malaise(Lasting about 24 hrs)In adults, the prodromal illness is more severe and lasts longer
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13. 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
14. SECONDARY ATTACK RATE70-90 percentin susceptible siblings within a household
15. 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
16. * Natural infection confers lifelong immunity. * However, the virus can remain latent in sensory rootGanglia. *Reduction in cell mediatedimmunity can resultin reactivation of the virus which causes Herpes zoster in 10-30 percent cases. * Thedisease occurs with greater severity among adults, newborn infants, immunocompromised children and pregnant women.
17. COMPLICATIONS* Bacterial super infection of theskin ( 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
18. : Other Complications :* Acute cerebellar ataxia* Encephalitis* Varicellahemorrhagical* Corneal lesions* Myocarditis* Reye’s syndrome* Arthritis* Ac. Glomerulo nephritis Mortality is less than 1% in uncomplicated cases.
19. 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.
21. : 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.
22. :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 dressingsAntipruritic drugs
23. 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)
24. PREVENTION1. VZIGvaricella 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
25. 2. VACCINE (Live attenuated varicella virus vaccine) * Recommended for 12-18 monthschildren who have not had Chickenpox. * Persons above 12 years need 2 doses 4-8 wks apart. * Duration of immunity is probably 10 years.
26. * The vaccine is90%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
27. ADVERSE REACTIONS OF VACCINE* Tenderness & erythema at injection site (25 % )* Fever ( 10-15% )* Localized maculopapular rash ( 5% )
28. CONTRAINDICATIONS TO VACCINE* Pregnancy* Immunodeficiency* Allergy to Neomycin* Salicylates should be avoided for 6 weeks following vaccination
