EPIDEMIOLOGY OF POLIO

1. EPIDEMIOLOGY
OF POLIO
DR. MAHESWARI JAIKUMAR.
maheswarijaikumar2103@gmail.com

2. POLIO is a vaccine preventable
communicable disease

6. PATHOLOGY
• The main pathology is in the
anterior horn cells.
• The polio virus affects the
anterior horn cells of the CNS

7. POLIO
• Poliomyelitis is
an acute viral
infection
caused by an
RNA virus.

8. • It is primarily an infection of
the human alimentary tract
but the virus may infect the
central nervous system. (1%)
of cases resulting in varying
degree of paralysis, and
possible death.

10. POLIO VIRUS AFFECTING
THE ANTERIOR HORN CELLS

11. EPIDEMIOLOGICAL
DETERMINANTS

12. AGENT
• The causative agent is the polio
virus which has three serotypes
1,2, and 3.
• Most outbreaks of paralytic polio
are due to type 1 virus.

14. • Polio virus can survive for long
periods in the external
environment.
• In a cold environment, it can live
in water for 4 months and in
faeces for 6 months.

15. • There fore the virus is well
adapted for faeco oral route of
transmission.
• However the virus can be rapidly
inactivated by pasteurization
and a variety of physical and
chemical agents.

16. RESERVOIR OF INFECTION
• Man is the only known reservoir
of infection.
• Most infections are subclinical.

17. • Mild and subclinical infections
play a dominant role in the
spread of infection; they
constitute the submerged
portion of iceberg.

18. • It is estimated that for every
clinical case there may be 1000
sub clinical cases in children and
75 in adults.
• There are no chronic carriers,
and no animal source has been
demonstrated.

19. INFECTIOUS MATERIAL
• The virus is found in the faeces
and oropharyngeal secretions of
an infected person.

20. PERIOD OF
COMMUNICABILITY
• The cases are most infectious 7
to 10 days before and after the
onset of symptoms.

21. • In faeces the virus is excreted
commonly for 2 to 3 weeks,
some times may extend up to 3
to 4 months.

22. HOST FACTORS
• AGE : The disease occurs in all
age groups, but children are
more susceptible.
• In India polio is essentially a
disease of infancy and
childhood.

23. GENDER
• Gender differences have been
noted in the ratio of 3 males to
one female.

24. RISK FACTORS
• Certain provocative or risk
factors have been have been
found to precipitate an attack
of paralytic polio in
individuals already infected
with polio virus.

25. • They are fatigue, trauma,
intramuscular injections,
operative procedures such as
tonsillectomy undertaken
during polio epidemics,
administering of immunizing
agents such as alum
containing DPT.

26. IMMUNITY
• The maternal antibodies
gradually disappear during
the first 6 months of life.

27. • Immunity following infection
is fairly solid although
reinjection can occur
(infection with one type does
not confer immunity against
the other types)

28. • Type 2 virus appears to be the
most effective antigen.
• Neutralizing antibody is
widely recognized as an
important index of immunity
to polio after infection.

29. ENVIRONMENTAL FACTORS
• Polio is likely to occur during
the rainy season.
• The environmental sources of
infection are contaminated
water, food, flies.

30. • Polio virus survives for a long
time in a cold environment.
• Overcrowding and poor
sanitation provide
opportunities for exposure to
infection.

31. MODE OF TRANSMISSION
1. FAECAL-ORAL ROUTE.
2. DROPLET INFECTION.

32. FAECAL-ORAL ROUTE
•This is the main route of
transmission in developing
countries.

33. • The infection may spread
directly through
contaminated fingers where
hygiene is poor, or indirectly
through contaminated water,
milk, foods, flies and articles
of daily use.

34. DROPLET INFECTION
•This may occur in the
acute during the acute
phase of the disease when
the virus occurs in the
throat.

35. • Close personal contact with an
infected person facilitates
droplet spread.
• This mode of transmission may
be relatively more important in
developed countries where
faecal transmission is remote.

36. INCUBATION PERIOD
• USUALLY 7 TO 14 DAYS (3 TO 35
DAYS)

37. CLINICAL SPECTRUM
• When an individual susceptible
to polio is exposed to infection,
one of the following responses
may occur.

38. INAPPARENT (SUBCLINICAL)
INFECTION
•This occurs approximately
in 91 to 96% of polio virus
infections.

39. •There are no presenting
symptoms and recognition
is done only by virus
isolation or rising antibody
titres.

40. ABORTIVE POLIO
•Is also called as minor
illness.
•Occurs approximately 4 to
8 % of the infections.

41. •It causes only a mild or self
limiting illness due to
viraemia.
•The patient recovers
quickly. Diagnosis cannot
be made clinically.

42. •Recognition only by virus
isolation or rising antibody
titre

43. NON PARALYTIC POLIO
• Occurs in approximately 1% of
all infections.
• The presenting features are
stiffness and pain in the neck
and back.

44. •The disease lasts for 2 to
10 days.
•Recovery is rapid. The
disease is synonymous
with septic meningitis.

45. PARALYTIC POLIO
•Occurs in less than 1% of
infections.
•The virus invades CNS and
causes varying degrees of
paralysis.

46. •The predominant sign is
asymmetrical flaccid
paralysis.
•A history of fever at the
time of onset of paralysis
is suggestive of polio.

47. •The other associated
symptoms are malaise,
anorexia, nausea,
vomiting, headache, sore
throat, constipation and
abdominal pain.

48. •There might be signs of
meningeal irritation, i.e.,
stiffness of neck and back
muscles.

49. • Tripod sign may be present.
(child finds difficulty in
sitting and sits by supporting
hands at the back and by
partially flexing the hips and
knees).

50. •Progression of the
paralysis to reach its
maximum in the majority
of cases occur in less than
4 days (may take 4-7 days).

51. •The paralysis is
characterized as descending.

52. • i.e., starting at the hip and
then moving down to the
distal parts of the extremity.
• As it is asymmetrical patchy
paralysis, muscle strength
varies in different muscle
groups of different limbs.

53. • However , proximal muscle
groups are more involved as
compared to distal ones.
• Deep Tendon Reflexes (DTRs)
are diminished before the
onset of paralysis.

54. •There is no sensory loss.
•Cranial nerve involvement
is seen in bulbar and
bulbospinal forms of
paralytic poliomyelitis.

55. •There might be facial
asymmetry, difficulty in
swallowing, weakness or
loss of voice.

56. • Respiratory insufficiency can
be life-threatening and is
usually the cause of death.

57. •After the acute phase,
atrophy of the affected
muscles lead to a life when
residual paralysis which is
typical and relatively easy
to identify as
poliomyelitis.

58. • Progressive paralysis, coma or
convulsions usually indicate a
cause other than polio, as
does a very high case fatality
rate.
• There is no specific treatment
for polio.

59. •Good nursing care from
the beginning of illness
can minimize or even
prevent crippling.
•Physiotherapy is of vital
importance.

60. • It can be initiated in the
affected limb immediately.
• It helps the weakened
muscles to regain strength.
Very probably the child may
have to put on metal
callipers.

61. PREVENTION
• Immunization is the sole
effective means of preventing
polimyelitis.
• Both killed and live attenuated
vaccines are available.

62. •Both are safe and effective
when used correctly.
•It is essential to immunize
all children by 6 months of
age to protect them against
polio.

63. • Two types of vaccines are used
globally.
1. INACTIVATED (SALK) POILO
VACCINE (IPV).
2. ORAL (SABIN) POLIO VACCINE
(OPV).

64. DR. JONAS SALK

65. IPV
• IPV is made from inactivated
WPV strains-namely,
Mahoney (Salk type-1), MEF-1
(Salk type-2) and Saukett (Salk
type-3).

66. •They are grown in Vero cell
culture or in human
diploid cells.

67. • Harvested viral components are
inactivated with formaldehyde.
• The final vaccine mixture is
formulated to contain atleast 40
units of type-1,8 units of type 2
and 32 units of type 3 D antigen.

68. •D-antigen refers to the
virus particles, is used to
adjust the concentration
of the individual viruses
included in the trivalent
IPV.

69. • IPV contains preservatives
such as phenoxy- ethanol
(0.5%).

70. •Thiomersal or any other
adjuvants are not used.
•IPV is administerd by IM
(preferred) or
Subcutaneous injection.

71. •The vaccine is stable at
ambient temperature, but
should be refregerated to
ensure no loss of potency.

72. • IPV is available either as a
stand-alone product or in
combination with >1 other
vaccine antigens including
diptheria, tetanus, whole-cell
or acellular pertussis,
hepatitis B, or haemophilus
influenzae type b.

73. •In combination vaccines,
the alum or the pertussis
vaccine, or both, have an
adjuvant effect.

74. •The primary or initial
course of immunization
consists 4 inoculations.

75. •The first 3 doses are given
at intervals 1-2 months
and the 4 dose 6-12
months after the third
dose.

76. •The first dose is usually
given when the infant is 6
weeks old. Additional
doses are recommended
prior to school entry and
then every 5 years until
the age of 18.

77. • IPV induces, humoral antibodies
(IgG, IgA, IgM serum antibodies)
but does not include intestinal
or local immunity.

78. •The circulating antibodies
protect the individuals
against paralytic polio, but
do not prevent infection of
the gut by wild viruses.

79. • The advantages of IPV includes
that it is inactivated and hence
it is safe to administer to
persons with immune
deficiency disease, individuals
undergoing corticosteroid and
radiation therapy and during
pregnancy.

80. OPV
• Oral Polio vaccine was
described by Sabin in 1957.
• It contains live attenuated
virus (type 1,2, and 3) grown
in primary monkey kidney or
human diploid cell cultures.

81. DR. ALBERT SABIN

83. •For administrative reasons
it is given as trivalent
(TOPV) vaccine : which
contains type 1,2 & 3
strains.

84. • The vaccine contains the
following.
• 3,00,000 TCID 50 of type 1 polio
virus per dose.

85. • Over 1,00,000 TCID 50 of
type 2 polio virus per dose.
• Over 3,00,000 TCID 50 of
type 3 polio virus per dose.

87. NATIONAL IMMUNIZATION
SCHEDULE
•3 doses of OPV at one
month interval is
recommended to infants
under the national
immunization schedule.

88. • Following these three doses
booster dose is administered at
one and half a year 12 to 18
months.

90. •The first dose is
administered when the
infant is 6 weeks old.

91. •It is recommended that a
dose of OPV (zero dose) is
required to be given to all
children delivered in
health institutions before
their discharge from the
hospital.

92. •The vaccine should be
given in maternity ward
and the child should not
be taken to the
immunization OP to avoid
other infections.

93. DOSE AND MODE OF
ADMINISTRATION
• The dose is 2 drops or as
stated on the label.

94. • WHO recommends that
vaccinators use dropper
supplied with the vial of OPV.

95. •This is the direct and the
most effective way to
deliver the correct drop
size.

96. • Tilt the child’s back, and
gently squeeze the cheeks or
pinch the nose to make the
mouth open.

97. •Let the drops fall from the
dropper onto the child’s
tongue.
•Repeat the process if the
child spits out the vaccine.

98. •If the vaccine is spoon fed
there is a chance that it
will not be licked up by the
child.

99. • On administration, the live
vaccine strains infect
intestinal epithelial cells

100. •After replication, the virus
is transported to the
Peyer’s patches where a
secondary multiplication
with subsequent viraemia
occurs.

101. • The virus spreads to the
other areas of the body,
resulting in the production
of circulating antibodies
which prevent the
dissemination of the virus to
the nervous system and
prevents paralytic polio.

102. • Intestinal infection stimulates
the production of IgA secretory
antibodies which prevent
subsequent infection of the
alimentary tract with wild strains
of polio virus, and thus is
effective in limiting virus
transmission in the community.

103. •Thus OPV induces both
local and systemic
immunity.

104. • The vaccine progeny is
excreted in the faeces and
secondary spread occurs to
household contacts and
susceptible contacts in the
community.

105. •Non immunized persons
may therefore, be
immunized.
•Thus widespread “HERD
IMMUNITY” results.

106. • This property of OPV is
exploited in controlling
epidemics of polio.

107. •This procedure virtually
eliminates the wild polio
strains in the community
and replaces them by
attenuated strains.

108. •Breast feeding is not
contraindicated for
administration of OPV.

109. ADVANTAGES
•Since given orally, it is easy
to administer and does not
require the use of highly
trained manpower.

110. • Induces both humoral and
intestinal immunity.

111. •Antibody is quickly
produced in a large
proportion of vaccinees,
even a single dose elicits
substantial immunity.

112. • OPV is free from
complications. (occasionally
paralytic polio have occurred
among the recipents)

113. CONTRAINDICATIONS
•Diarrhoea is not
considered as a
contraindication.

114. STORAGE STABILIZED
VACCINE
•Recent polio vaccines are
heat stabilized by adding
magnesium chloride.

115. • They can be kept without
losing potency for a year at 4
deg C and for a month at 25
deg C temp.

116. STORAGE OF NON
STABILIZED VACCINE
•The vaccine should be
stored at -20 deg C in a
deep freeze until used.

117. • In case a deep freezer is not
available, it might be stored
temporarily in a freezing
chamber of a refrigerator.

118. •In case a deep freezer is
not available, it might be
stored temporarily in a
freezing chamber of a
refrigerator.

119. • During transport the vaccine
must be kept either on dry
ice (solid carbon dioxide) or
a freezing mixture (equal
quantities of wet ice and
ammonium chloride).

120. • At the vaccination clinic, the
bottle containing the OPV
should not be frozen and
thawed repeatedly, since
repeated freezing and
thawing has deleterious effect
on the potency of the live
polio vaccine.

121. •It would be preferable to
keep vials of the vaccine in
ice during its
administration to children.

122. • Breast feeding does not
impede the effectiveness of
the vaccine.

123. VACCINE CARRIER

124. •However when the child is
hungry, hot milk or hot
fluids should be withheld
for half an hour before and
after the administration of
the vaccine.

125. •The vaccine should be
administered preferably in
a cool room, rather than in
a hot, humid and crowded
room.

126. OPV/IPV
OPV (SABIN TYPE) IPV (SALK TYPE)
LIVE ATTENUATED
VIRUS
KILLED
FORMALIZED
VIRUS
GIVEN ORALLY GIVEN IM/SC

127. OPV (SABIN TYPE) IPV (SALK TYPE)
IMMUNITY IS BOTH
HUMORAL &
INTESTINAL.
INDUCES
CIRCULATING
ANTIBODIES, BUT NO
LOCAL IMMUNITY
INDUCES ANTIBODY
QUICKLY
…….

128. OPV (SABIN TYPE) IPV (SALK TYPE)
PREVENTS NOT ONLY
PARALYSIS BUT ALSO
INTESTINAL RE
INFECTION
PREVENTS PARALYSIS,
BUT DOES PREVENT
REINFECTION BY
WILD POLIO VIRUS

129. OPV (SABIN TYPE) IPV (SALK TYPE)
CAN BE EFFECTIVELY
USED IN
CONTROLLING
EPIDEMICS. EVEN A
SINGLE DOSE ELICITS
SUBSTANTIAL
IMMUNITY.
NOT USEFUL IN
CONTROLLING
EPIDEMICS

130. OPV (SABIN TYPE) IPV (SALK TYPE)
EASY TO
MANUFACTURE
MORE DIFFICULT TO
MANUFACTURE
CHEAPER THE VIRUS CONTENT
IS 10,000 TIMES
MORE THAN OPV.
HENCE COSTLIER

131. OPV (SABIN TYPE) IPV (SALK TYPE)
REQUIRES TO BE
STORED AND
TRANSPORTED AT
SUB-ZERO
TEMPERATURES,
UNLESS STABILIZED
DOES NOT REQUIRE
STRINGENT
CONDITIONS DURING
STORAGE AND
TRANSPORTATION .
HAS LONGER SHELF
LIFE

132. STRATEGIES FOR POLIO
ERADICATION IN INDIA
• Conduction of Pulse Polio
Immunization days every year
until polio is eradicated.
• Sustain high levels of routine
immunization.

133. • Monitor OPV coverage at
dist level and below.
• Improve surveillance capable
of detecting all cases of AFP
due to polio and non polio
aetiology.

134. • Arrange follow up of all cases
of AFP at 60 days to check
samples for virus isolation.
• Conduct outbreak control for
cases confirmed or suspected
to be polio to stop
transmission.

135. •Other activities include :
line listing of cases,
mopping up, and
implementation of Pulse
Polio Programme.

137. THANK YOU