Pox (small, chicken)

Dr. S. A. Rizwan M.D.,Assistant Professor,

Dept. of Community Medicine,VMCHRI, Madurai.

Learning objectives

• At the end of this lecture you sh be able to– Describe the epidemiological triad and the

prevention aspects of these infections– Understand the factors that contribute to

epidemics– Enumerate the factors that led to eradication of

small pox– Enumerate the differences between the two

SMALL POXபெ�ரியம்மை�

Introduction

• Smallpox is a serious, contagious and sometimes fatal disease

• At its height, 10-15 million cases a year, with 2 million deaths

• There is no specific treatment for smallpox, and the only prevention is vaccination.

• The name smallpox is derived from the Latin word “spotted” and refers to the raised bumps that appear on the face and body of an infected person.

• It is caused by variola virus, Orthopoxvirus genus

History

• Mummified remains of Ramses. (1157 B.C.)• Smallpox was likely carried from Egyptian

traders to India • By 1967 it became a major killer in not less

than 33 countries• Those who survive became immune • As a result, physicians intentionally infected

healthy persons with smallpox organisms

Variolation

• It is the act of taking samples (pus from pustules or ground scabs) from patients whose disease had been benign, and introducing it into others through the nose or skin

Edward Jenner

Jenner’s contribution• He found that, the cowpox would protect the patient

from smallpox• He proposed it in 1798• In England vaccination with cowpox became

compulsory in 1853

• Jenner was honored for his technique, and ‘Vaccine’ became the universally used term to indicate introducing material under the skin to produce a protection against disease

Variola virus

Transmission

• Humans are the only natural host of smallpox (no animal reservoir)

• Transmission generally occurs from direct and fairly prolonged face-to-face contact

• Infected aerosols and air droplets spread in face-to-face contact

Pathogenesis

• Portal of entry: respiratory tract or inoculation on skin

• Source of infection: Excretions from the mouth and nose, rather than scabs

• During incubation the virus proceeds through infection, replication, and liberation (usually accompanied by cell necrosis) first at the site of inoculation and then to the regional lymph nodes, then deeper lymph nodes and bloodstream

Pathogenesis

• 4 orthopoxviruses are known to infect humans: variola, vaccinia, cowpox, and monkeypox

• Variola major is severe and the most common form with more extensive rash and higher fever with a death rate of 30%

• Variola minor has less common presentation and much less severe with death rate of 1%

Pathogenesis

• Variola Major has 3 clinical presentations based on the nature and evolution of the lesions:

– Ordinary: most frequent, corresponds to classical description

– Modified: milder and may occur in previously vaccinated people; rarely fatal

– Flat and Hemorrhagic: very severe but uncommon

Stages of Smallpox• Incubation Period

– 12-14 days, person is not contagious• Prodrome Phase

– Begins abruptly with fever, malaise, headache, head and body aches, prostration, and often nausea and vomiting

– Body temperature rises to at least 101 F and is often higher

• When the first visible lesions appear the fever may start to go down - most contagious period

• Rash emerges as small red spots on tongue and in mouth (about 24 hours before the appearance of rash on the skin)

• Lesions in the mouth and pharynx enlarge and ulcerate quickly, releasing large amount of virus into the saliva

Stages: Rash Phase

• Centrifugal distribution

• Palms and soles are involved

• lesions are all in the same stage of development on that part of the body (unlike chickenpox)

Outcomes of infection

• Those who survive usually have scars• In eye involvement, blindness could occur• Recovery results in long lasting immunity• No evidence of chronic or recurrent infection

Vaccination• Live vaccinia virus• Administered using a

bifurcated needle, not an injection

• Bifurcated needle is dipped into the vaccine and then used to prick the skin 15 times in about 3 seconds in a 5mm radius area

• Administered into the superficial layer of the skin

Course of vaccination• If vaccination is successful a red, itchy bump develops at the

vaccine site in 3-4 days; a papule surrounded by erythema

• In the first week the bump becomes a blister, fills with pus, and begins to drain

• During the second week the blister begins to dry and a scab forms; the scab then falls off leaving a scar

• It is given on the right side universally

A reminder of the small pox era

Control

• Only after WWI most of Europe become smallpox free, and only after WWII transmission stopped throughout Europe and North America

• In developing countries smallpox continued largely unabated until middle of 20th century

Control

• 1958: Soviet Union proposed to the WHO that a global smallpox eradication program be undertaken

• The campaign was based on a two fold strategy– 1. Mass vaccination campaigns in each country using a

vaccine of ensured potency and stability that would reach at least 80% of the population

– 2. Surveillance-Containment - isolation of patients and the vaccination of family members and other contacts in the immediate vicinity

Control

• Ring vaccination:• Incorporated into the current CDC Smallpox Plan• The strategy involves the following steps:– Rapid identification and isolation of all smallpox cases– Identification and vaccination of contacts of smallpox

cases– Monitoring contacts for development of fever and

isolating them if fever occurs– Vaccination of household members of contacts if no

contraindications to vaccination exist

Management of an outbreak

• Surveillance is easier because of the distinctive rash• Containment involves efficient detection of cases and

identification and vaccination of contacts• Patients diagnosed with smallpox should be physically

isolated• All specimen collectors, care givers and attendants

coming into close contact with patients should be vaccinated

• Medical care givers, attendants, and mortuary workers should wear gloves, caps, gowns, and surgical masks

Management of an outbreak

• Contaminated clothing and bedding, if not incinerated, should be autoclaved or washed in hot water containing bleach

• Fumigation of premises with formaldehyde• Airborne and Contact Precautions in addition

to Standard Precautions should be implemented for patients with suspected smallpox

Eradication

• In India• Last case reported on 17th May 1975 in Bihar• On 24th May 1975, imported from Bangladesh• In April 1977 declared free from smallpox

Eradication

• 26th October 1977 the last naturally occurring case of smallpox was recorded in Somalia

• In 1978 two cases were reported. These were both from people working in labs with smallpox in England

• 8th May 1980, WHO declared that smallpox has been eradicated

Factors that led to eradication

• Epidemiological factors:– No known animal reservoir– No long-term carrier of the virus– Life-long immunity after recovery from the disease– Detection of cases, the rash was so characteristic– Sub-clinical infection did not transmit the disease– Vaccine highly effective– International co-operation

CHICKEN POXசின்னம்மை�

Introduction

• Acute, highly infectious disease caused by Varicella-Zoster (V–Z) virus

• Chicken pecked skin appearance, chickpea appearance

• World-wide in distribution and occurs in endemic and epidemic forms

• Chickenpox and Herpes zoster as different host responses to the same etiological agent

• In India, approx. 28,000 cases per year

Epidemiological determinants

• Agent: Human (alpha) herpes virus– Primary infection causes chicken pox– Recovery followed by latent infection– Reactivation results in zoster- a painful, vesicular,

pustular eruption in distribution of one or more sensory nerve roots

– Can be grown in tissue culture• Incubation period: 14-16 days (7-21 days)

Source of infection

• Usually a case of chicken pox• Virus present in oropharyngeal secretions and

lesions of skin and mucosa• Rarely may be a patient with herpes zoster• It can be isolated from the vesicular fluid

during the first 3 days of illness

Infectivity

• Period of communicability: 1-2 days before the appearance of rash, and 4-5 days thereafter

• It tends to die out before the pustular stage• Patient ceases to be infectious once the lesion

have crusted• Secondary attack rate: About 90% in

household contacts

Host factors

• Age– Children under 10 years of age– Few escape until adulthood but can be severe in adults

• Immunity– One attack give durable immunity– Maternal antibody protects the infant for few months– No age is exempt in the absence of immunity– IgG antibodies persist for life and correlate with protection – Cell mediated immunity is important in recovery

• Pregnancy: Risk for fetus and neonate

Environmental factors

• It shows a seasonal trend, occurring mostly during the first six months of the year

• Overcrowding• In temperate climates, there is little evidence

of seasonal trend

Transmission

• Droplet infection and droplet nuclei• ‘Face to face’ (personal) contact• Portal of entry: respiratory tract• Virus is extremely labile, so fomites unlikely to

transmit• Contact infection plays a significant role when an

individual with herpes is an index case• Congenital varicella - it crosses the placental

barrier and infects the foetus

Clinical features

• Clinical spectrum– Mild illness with few scattered lesions – Severe febrile illness with widespread rash

• Pre-eruptive stage– Sudden onset with mild to moderate fever– Pain in the back, shivering and malaise– Duration about 24 hours– In adults, prodromal illness is usually more severe

and may last for 2-3 days before the rash

Clinical features

• Eruptive stage: in children the rash comes on day the fever starts and first sign

• The distinctive features of rash are– Rash is symmetrical– Appears on the trunk and then comes to face, arms ,legs– Mucosal surfaces (buccal, pharyngeal) are involved– Axilla affected. Palms and soles usually not involved– The density of eruption diminishes centrifugally– Pleomorphism - All stages of rash (papules, vesicles and

crusts) may be seen simultaneously in the same area

Clinical features

• Evolution of rashes– The rash advances quickly through the stages of- macule papule vesicle scab– Vesicles filled with clear fluid resembling ‘dew-drops’– Superficial in site, with easily ruptured walls and

surrounded by an area of inflammation– Vesicles may form crusts directly. Many lesions may abort– Scabbing begins 4-7 days after the rash appears

• Fever not high but exacerbations with fresh crop

Complications

• It’s a mild, self-limiting disease• Patients at risk of complications are – Immunosuppressive patients– Cancer patients – Recipients of organ transplants– Chemo, radio, steroid therapy recipients– HIV infected– Children with leukemia

Complications• Haemorrhages (varicella haemorrhagica)• Pneumonia• Encephalitis• Acute cerebellar ataxia• Reye’s syndrome• Maternal varicella may cause foetal wastage & birth defects• Acute retinal necrosis• Secondary bacterial infections (Cellulitis, erysipelas,

epiglottitis, osteomyelitis, scarlet fever and meningitis)• Pitted scars

Congenital defects in babies • Damage to brain: encephalitis, microcephaly, hydrocephaly,

aplasia of brain • Damage to the eye: microphthalmia, cataracts, chorioretinitis,

optic atrophy• Other neurological disorder: damage to cervical and

lumbosacral spinal cord, motor/sensory deficits, absent deep tendon reflexes, anisocoria/Horner's syndrome

• Damage to body: hypoplasia of upper/lower extremities, anal and bladder sphincter dysfunction

• Skin disorders: (cicatricial) skin lesions, hypo pigmentation

Laboratory diagnosis• Most rapid and sensitive

– Examination of vesicle fluid under electron microscope

– Round particles which may be used for cultivation

• Scrapings of floor of vesicles show multinucleated giant cells coloured by Giemsa stain

• Serology for epidemiological surveys

Control

• No specific treatment for chicken pox• Notification• Isolation of cases for about 6 days after onset of

rash• Disinfection of articles soiled by nose and throat

discharges• Antiviral drugs provide effective therapy for

varicella (acyclovir, valaciclovir, famiciclovir and foscarnet)

Prevention

• Varicella zoster immunoglobulin (VZIG)• VZIG given within 72 hours of exposure has

been recommended for prevention– Dosage: 1.25-5ml intramuscularly– Used for immunosuppressed contacts of acute

cases or newborn contacts– Provide improvement in high risk children with

varicella

Vaccine

• Live attenuated vaccine (Japan)• Mild local reaction at inoculation site is 1%• A general reaction mainly rash or mild

varicella may occur• Seroconversion in healthy seronegative

children is over 90%• Age shift of peak incidence due to vaccinations

is a major concern

Vaccine

• Monovalent vaccine • One or two dose schedule (0.5 ml subcutaneous

injection)• For children between 12-18 months• Two dose schedule for persons aged >13 years • Minimum interval between doses 6 weeks • Combination vaccines (MMRV) for children 9

months to 12 years • Duration of immunity probably 10 years

Difference between pox (small, chicken)

Difference between small pox and chicken pox

Small pox Chicken poxIncubation 12 days (7-17) 15 days (7-21)Prodromal Severe Mild Distribution of rash Centrifugal Centripetal

Palms and soles involved Not involvedAxilla free Axilla affectedExtensor surfaces Flexor surfaces

Characteristics of rash Deep seated SuperficialMultilocular, umbilicated Unilocular, dew dropOne stage at a time Pleomorphic No inflammation around the vesicles

Inflammation seen

Difference between small pox and chicken pox

Small pox Chicken poxEvolution of rash Slow and majestic,

passing through definite stages of macule, papule, vesicle and pustule

Very rapid

Scabs 10-14 days Scabs in 4-7 daysFever Subsides with

appearance of rash, may rise again at the pustular stage

Fever appears with each fresh crop of rash

Review 1

• Infectivity of chicken pox lasts fora) Till the last scab falls offb) 6 days after onset of rashc) 3 days after onset of rashd) Till fever subsides

Review 2

• Chicken pox is characterized by all except a) Scabs are infectiveb) Pleomorphic stagesc) Rashes symmetrical centripetal dew drop liked) Palms and soles not affected by rash

Review 3

• Small pox eradication was successful due to all of the following reasons excepta) Subclinical cases did not transmit the diseaseb) A highly effective vaccine was availablec) Infection provided lifelong immunityd) Cross resistance existed with animal pox

Review 4

• All of the following are true about varicella virus excepta) 10-30% chance of recurrenceb) All stages of rash seen at the same timec) Secondary attack rate is 90%d) Rash commonly seen in flexor area

Review 5

• All of the following are true about varicella virus excepta) Lesions appear in cropsb) Centripetal distribution of rashesc) Rashes shows rapid progression from macule to

vesicled) Crusts contain live virus

Review 6

• What is the difference between vaccination and variolation?

Review 7

• When was the last case of small pox in India identified and when was it declared small pox free?

Review 8

• When was the world declared free of small pox?

Review 9

• Why is small pox called class blind?

Review 10

• Can small pox infection occur in the world today?

• If yes, what will be the consequences?

THANK YOU