CHICKEN POX&SMALL POX Edited by: Dr: HALA ALI ABED Lecturer of public health

 Definition of the disease( bacterial,viral, zoonotic ……….etc).  Magnitude of the problem.  Epidemiology of the disease: Agent. Reservoir: man only, animal only or man& animal. Mode of transmission. Incubation period. Susceptibility:

Distribution of the disease according to time, place person. * Immunity: natural( active& passive) and acquired (active& passive). * Herd Immunity. Diagnosis : - Clinical picture, complication and investigation.  Prevention  Control

CHICKEN POX

Epidemiology Acute viral disease of children characterized by skin rash (centripetal and pleomorphic). Chicken pox is also called varicella. Causative agent: Varicella Zoster (V-Z) virus Reservoir:(man only) Cases of varicella or herpes zoster: (V-Z) virus in the respiratory secretions and fluid of skin rash.

Mode of transmission:  Direct droplet infection (cough spray).  Droplet nuclei (air-borne).  Contact infection (fluid of vesicles).  Articles and fomites (by fluid of vesicles or respiratory tract discharge).  Exposure to a case of herpes zoster

Incubation period: 2-3 weeks. Communicability period: Throughout the disease “1” day before and “7” days after appearance of skin rash.

Clinical picture  Prodroma: Fever, headache and malaise.  Skin rash:  Centripetal: more on the abdomen.  Pleomorphic: all stages of rash present, macules, papules, vesicles, pustule, crusts and scabs that fall off within one week Complications  Secondary infection of vesicles.  Pneumonia.  Encephalitis, rare.  Fatality: rare

Diagnosis: Clinical picture. Lab-isolation of virus by tissue culture of vesicles – fluid. “To exclude small pox when suspected”.

Susceptibility : Infant born to immune mothers have passive immunity. Children (sporadic cases or outbreaks). Adults may be affected (severe disease). Vaicella zoster IgG modify or preventing disease if given withen 4days after exposure. Durable immunity( virus remain latent, and disease may recure years later as herpes zoster in 15% of older adult.

Prevention: 1- general prevention measures: for prevention of respiratory diseases. 2- specific: A.Vaccine: Type: live attenuated vaccine. Adminsteration: 0.5 ml s.c Immunity: 85%-90% for prevention of disease. 100%for prevention of severity.

Target group: -children aged 18 months and up to 12 y who have not varicella before -contact of cases: if given within 3 days of exposure. Susceptible persons ˃ 13y e.g: health worker(2 doses,4-8 weeks apart. B. Seroprohylaxis: by specific immunoglobulin, to high risk close contacts (prematures and debilitated children).

Control: a- Cases Notification, Isolation(isolate children from school for 1 week after 1 st appearance of the rash or until vesicles become dry)., & Disinfection ( concurrent an terminal). Symptomatic treatment: to relieve irritation of skin and prevent infection Release: one week after appearance of rash (when rash disappears).

b- Contacts: -Enlistment, surveillance( for maximum i.p) - vaccine is given 3days after exposure if they are not vaccinated. Seroprophylaxis for high- risk contacts. And for newborns of mothers who develop chicken pox around delivery.

SMALL POX VARIOLA

Acute infectious disease characterized by generalized skin rash, it has been eradicated from the world (1978). Causative agent: Variola virus. Resistant to glycerol. Destroyed by heat, potassium permanganate. Survives several months in crusts of eruption

Reservoir Cases: Virus in respiratory discharges and skin rash. Incubation period: About 14 days (international)

Mode of transmission:  Direct droplet infection.  Droplet nuclei and crusts (air-borne).  Contact infection.  Contaminated articles & fomites. Communicability From onset of disease till disappearance of rash (2-3 weeks).

Clinical picture: 1- Prodroma: Fever, headache and backache (sudden). 2- Skin rash: Appears at the end of 3rd day of disease. First on the face and then covers the body in 2-3 days. Characterized by being: - Centrifugal : more on face and extremities. - More on extensor than flexor surfaces (maxillae free). - More at areas of pressure.

- Monomorphic: only one stage present, the Stages of rash are macules & papules. Vesicles, pustules, crusts, Fall off at the end of 3rd w causing scar (permanent scar) - Enanthema: Eruption of mucous membranes of mouth, tongue, nose, pharynx, larynx and other parts may be present.

Types 1- Variola major: with different forms of rash and severity - Discrete. - Confluent: extensive, severe rash fatal. - Hemorrhagic: very high fatality. 2- Variola minor (alastrim): Mild fever may simulate chickenpox but it is centrifugal and monomorphic. 3- Varioloid: A mild form. In vaccinated cases, conjunctivitis and corneal ulcer, mucosal ulcers, pneumonia and bronchopneumonia.

Diagnosis: Clinical: Prodroma and typical skin rash. Laboratory: - Stained smears from vesicles and pustules. - Chick embryo culture (from blood and fluid of eruption). - Paul’s test on rabbit cornea fluid of vesicles on scarified rabbit cornea produces vesicles on rabbit cornea.

Prevention: By: (I) immunization. (II) International measures. Control: a-Case: * Notification: even in suspected cases. * Isolation in hospital. * Disinfection. * Treatment. * Release: after all scabs disappear.

b- Contacts: - Vaccination. - Surveillance for 2 weeks. c- Epidemic measures: ► Trace source and channels of infection. ► Mass vaccination of the area.