CHICKEN POX&SMALL POX Edited by : Dr: HALA ALI ABED Lecturer of public health
CHICKEN POX&SMALL POXEdited by:
Dr: HALA ALI ABEDLecturer of public health
To describe any infectious disease, you should comment on:
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 1st 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 POXVARIOLA
• 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.