2. Smallpox (Variola)
1st disease been ERADICATED from India
Milestones-
– May 1975- last case in India (Bihar)
– April 1977- India declared smallpox free
– Oct 1977- World’s last case (Somalia)
– 1978 – Laboratory accident
– 8th May 1990- WHO declaration on smallpox
eradication .
3. Smallpox
Acute infectious disease caused by Veriola virus
Fever of sudden onset with Centrifugal rash on
3rd day- characteristic,
headache,
backache,
vomiting,
sometime convulsion in child
4. Smallpox
Smallpox eradication – Golden
milestone in history of 20th century
SmPx eradication –leads to prevention of
– 2 million deaths,
– few lakhs cases of blindness,
– 10-15 million cases of smallpox
disease
7. Epidemiological factors which led to eradication of smallpox:
S- subclinical cases (total absent) - persons with
subclinical cases don't transmit disease
M- mutual (international) co-operation
A- attack rate (Secondary A R) rare
L- lifelong immunity after recovery from disease, lack
of animal reservoir
L- layman also can detect & report cases due to
characteristic & simple rash
P- person (human) not a carrier
O- outbreaks –slow transmission
X- vaccine- potent, stable, highly effective, confers
long term protection
8. Current status
2017- 40th anniversary of smallpox free status in
India (1997-was 20th anniversary)
smallpox eradication surveillance
Laboratory stocks still maintained in Us (Atlanta) &
Russia (Moscow)
Because the pox viruses like
– monkey pox,
– cow pox,
– camel pox,
– tanapox etc whose natural histories are not known exists.
In case of an outbreaks stocks will enable comparative
studies on these animal pox viruses
9. Future
2 potential sources of pox virus infection for
humans exists
This could be –
I. Accidental infection from laboratory stocks or
II. Infection with animal pox viruses
2 pox viruses-
– monkey & tena pox have attracted attention as potentially
capable of infecting humans
300 million vaccine stocks & bifurcated
needles are maintained by WHO as protective
measure
13. – Recovery from primary infection- followed
by latent infection in sensory ganglia after
decades without clinical manifestation,
When cell mediated immunity wanes with
age , immunosuppressive therapy-
– virus reactivate – resulting in Zoster- a
painful, vesicular, pustular eruption on
one / more sensory nerve roots
14. b) Source of inf-
Case of chicken pox & rarely patients with
herpes zoster
Virus occurs in oropharyngeal secretions
& lesions of skin & mucosa
Scabs not infective
Virus isolated from vesicular fluid- during
first 3 days of illness
15. c) Infectivity-
– 1-2 days before rash & 4-5 days after rash
d) Secondary attack rate-
– Highly communicable disease ,
– SAR in household contact 90%
e) Mode of spread-
– Direct contact,
– Droplet or air borne infection
– Face to face (personal contact)
16. f) Incubation period-
– 14-16 days (15 days)
g) Portal of entry- resp. tract
h) Placental barrier-
– crossed by virus-
– infect fetus- congenital vericella
17. Host factors-
1. Age-
children <10 yrs, may be until adulthood
2. Pregnancy-
infection during pregnancy risk factor for
fetus & neonate
18. 3. Immunity-
one attack give durable immunity,
second attack rare
Maternal antibody protect in first few months
of life
IgG antibodies protective against vericella
Cell mediated immunity important in recovery
from v-z infection
19. Environmental factors-
This shows seasonal trend in India
Common occurrence in first 6 months of yr
(Jan-May)
Overcrowding favors transmission
20. Clinical features-
Mild to severe form
Two stages
1. Pre-eruptive stage-
Characterized by
sudden onset of fever- mild to moderate,
pain in back, shivering & malaise- last for 24
hrs
21. 2. Eruptive stage-
In children- first sign is Rash
Rash comes on day the fever starts
Characteristics of Rash are-
– ‘Centripetal distribution’-rash is symmetrical
– First appears on trunk, then to face, arms,
legs.
– Also mucosal surfaces (buccal, pharyngeal)
involved
– Axilla may be affected, but palm & soles not
22. ii) Rapid evolution-
– Rash advances quickly through stages of
-Macule – papule – vesicle – scab
– ‘Dew drop’ appearance – vesicles filled
with clear fluid on skin, surrounded by
area of inflammation & not umblicated
– Scabbing begins 4-7 days after rash
appears
23. iii) ‘Pleomorphism’ –
– characteristic feature of rash in chickenpox
– i.e. all stages of rash (macule, papule, vesicle,
crust)-
– seen simultaneously at one time, in same area,
due to successive crops in 4-5 days.
iv) fever-
– usually exacerbations (increase temp) with each
fresh crop of eruption
24. Complications-
– Usually mild, self limiting
– Mortality < 1% in uncomplicated cases
– In immunosuppressive cases-
pneumonia, hemorrhage, encephalitis,
– Reye’s syndrome (acute encephalopathy with
fatty degeneration of liver), congenital vericella
– Maternal vericella- fetal wastage, birth defect,
microcephally, oncogenecity
29. Laboratory diagnosis-
1. Clinical signs
2. Examination of vesicle fluid-
– immunofluroscent staining of vesicular
scarping
– Serological tests in epidemiological surveys
30. Control-
No specific treatment- (Antiviral-Azovir suspension
in children just to reduce the severity?)
Notification-
Isolation - of cases for about 6 days
after onset of rash
Disinfection – of articles soiled nose &
throat discharges
31. Prevention-
1. Passive immunization-
Vericella-zoster immunoglobulin (VZIG)-
ideally given within 3 days,
if not at least within 7 days
125 – 600 IU (1.5 – 5ml IM) as per body wt.
Reserved for immunocompromised contact / newborn
contact / pregnant woman / pt. with leukemia
Prevents or modifies disease
32. 2. Active immunization
Vericella vaccine-
Live attenuated OKA strain, Japan
Available as lyophilized powder
Dissolve in 0.5 ml diluent
12 mon – 12 yr – single Subcutaneous injection
>13 yrs- 2 dose- 4-6 wks apart
Efficacy- 95-99%
No booster needed
Prevents disease in >80% of exposed, if administered
within 3 days of exposure
33. Chickenpox
IP- 15 days
Prodormal - usually mild
Distribution OF Rash-
– CENTRPETAL
– AXILLA AFFECTED
– PALM & SOLE SELDOM
AFFECTED
– RASH MOSTLY ON FLEXOR
SURFACE
Smallpox
IP- 12 days
Prodormal sympt- severe
Distribution OF Rash-
– CENTRIFUGAL
– AXILLA USUALLY FREE
– PALM & SOLE
FREQUENTLY INVOLVED
– RASH MOSTLY ON
EXTENSOR/BONY
SURFACE
34. Chickenpox
Characteristics of
Rash-
– Superficial
– Unilocular, Dew drop
like
– Pleomorphic rash- one
time
– Inflamed area – around
Smallpox
Characteristics of
Rash-
– Deep seated
– Multilocular, umblicated
– Only one stage at one
time
– No inflamed area –
around
35. Chickenpox
Evolution of Rash-
– Very rapid
– Scab begin to form 4-7
day after rash
appearance
Fever-
– Temp rises with each
fresh crop of Rash
Smallpox
Evolution of Rash-
– Slow, passes definite
sages of M, P, V, Pustule
– Scab begin to form 10-14
day after rash appearance
Fever-
– Fever subside with
appearance of Rash, but
rise again in Pustular
stage (secondary rise of
fever)
