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.