The document provides information on smallpox (variola) and chickenpox (varicella). It describes the epidemiology, clinical features, transmission, prevention and control of both diseases. Key differences between smallpox and chickenpox are enumerated. Smallpox was eradicated through a global vaccination program due to factors like no animal reservoir, effective vaccine, and lifelong immunity after infection. Chickenpox is generally a mild self-limiting disease caused by the varicella zoster virus.

1. Pox (small, chicken)
Dr. S. A. Rizwan M.D.,
Assistant Professor,
Dept. of Community Medicine,
VMCHRI, Madurai.

2. 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

3. SMALL POX
பெரியம்மை

12. 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

13. 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

14. 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

15. Edward Jenner

16. 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

17. Variola virus

18. 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

19. 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

20. 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%

21. 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

23. 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

24. 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)

27. 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

28. 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

30. 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

31. A reminder of the small pox era

32. 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

33. 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

34. 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

36. 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

37. 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

38. 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

39. 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

40. 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

41. CHICKEN POX
சின்னம்மை

42. 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

43. 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)

44. 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

45. 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

46. 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

47. 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

48. 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

49. 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

50. 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

52. 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

54. 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

55. 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

56. 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

57. 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

58. 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)

59. 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

60. 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

61. 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

62. Difference between pox (small, chicken)

63. Difference between small pox and
chicken pox
Small pox Chicken pox
Incubation 12 days (7-17) 15 days (7-21)
Prodromal Severe Mild
Distribution of rash Centrifugal Centripetal
Palms and soles involved Not involved
Axilla free Axilla affected
Extensor surfaces Flexor surfaces
Characteristics of rash Deep seated Superficial
Multilocular, umbilicated Unilocular, dew drop
One stage at a time Pleomorphic
No inflammation around
the vesicles
Inflammation seen

64. Difference between small pox and
chicken pox
Small pox Chicken pox
Evolution 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 days
Fever Subsides with
appearance of rash,
may rise again at the
pustular stage
Fever appears with
each fresh crop of rash

65. Review 1
• Infectivity of chicken pox lasts for
a) Till the last scab falls off
b) 6 days after onset of rash
c) 3 days after onset of rash
d) Till fever subsides

66. Review 2
• Chicken pox is characterized by all except
a) Scabs are infective
b) Pleomorphic stages
c) Rashes symmetrical centripetal dew drop like
d) Palms and soles not affected by rash

67. Review 3
• Small pox eradication was successful due to all
of the following reasons except
a) Subclinical cases did not transmit the disease
b) A highly effective vaccine was available
c) Infection provided lifelong immunity
d) Cross resistance existed with animal pox

68. Review 4
• All of the following are true about varicella
virus except
a) 10-30% chance of recurrence
b) All stages of rash seen at the same time
c) Secondary attack rate is 90%
d) Rash commonly seen in flexor area

69. Review 5
• All of the following are true about varicella
virus except
a) Lesions appear in crops
b) Centripetal distribution of rashes
c) Rashes shows rapid progression from macule to
vesicle
d) Crusts contain live virus

70. Review 6
• What is the difference between vaccination
and variolation?

71. Review 7
• When was the last case of small pox in India
identified and when was it declared small pox
free?

72. Review 8
• When was the world declared free of small
pox?

73. Review 9
• Why is small pox called class blind?

74. Review 10
• Can small pox infection occur in the world
today?
• If yes, what will be the consequences?

75. THANK YOU