Poliomylitis
Poliomylitis
Dr.
Dr.
Zahraa
Zahraa
A.Hassan
A.Hassan
·
·
Poliomyelitis
Poliomyelitis
(polio)
(polio)
is
is
a
a
highly
highly
infectious
infectious
disease
disease
caused
caused
by
by
a
a
virus
virus
that
that
invades
invades
the
the
nervous
nervous
system
system
,recognized
,recognized
by
by
acute
acute
onset
onset
of
of
flaccid
flaccid
paralysis
paralysis
.
.
·
·
The
The
site
site
of
of
paralysis
paralysis
depend
depend
on
on
location
location
of
of
nerve
nerve
cell
cell
destruction
destruction
in
in
the
the
spinal
spinal
cord
cord
or
or
brain
brain
stem
stem
,
,
legs
legs
are
are
affected
affected
more
more
than
than
the
the
arms
arms
,paralysis
,paralysis
of
of
the
the
respiration
respiration
and
and
/or
/or
swallowing
swallowing
muscles
muscles
can
can
be
be
life
life
threatening.
threatening.
Some
Some
improvements
improvements
in
in
paralysis
paralysis
may
may
occur
occur
during
during
convalescence
convalescence
,
,
but
but
paralysis
paralysis
still
still
present
present
after
after
60
60
days
days
likely
likely
to
to
be
be
permanents.
permanents.
Infectious
Infectious
agents
agents
·
·
Poliovirus
Poliovirus
is
is
an
an
RNA
RNA
virus
virus
a
a
member
member
of
of
the
the
enterovirus
enterovirus
subgroup,
subgroup,
family
family
Picornaviridae.
Picornaviridae.
·
·
There
There
are
are
three
three
poliovirus
poliovirus
serotypes
serotypes
(P1,
(P1,
P2,
P2,
and
and
P3)
P3)
,all
,all
cause
cause
paralysis
paralysis
but
but
mostly
mostly
1,less
1,less
commonly
commonly
3
3
and
and
rarely
rarely
2
2
,(2,3)
,(2,3)
are
are
associated
associated
with
with
vaccine
vaccine
polio.
polio.
There
There
is
is
minimal
minimal
heterotypic
heterotypic
immunity
immunity
between
between
the
the
three
three
serotypes.
serotypes.
That
That
is,
is,
immunity
immunity
to
to
one
one
serotype
serotype
does
does
not
not
produce
produce
significant
significant
immunity
immunity
to
to
the
the
other
other
serotypes
serotypes
.
.
·
·
The
The
poliovirus
poliovirus
is
is
rapidly
rapidly
inactivated
inactivated
by
by
heat,
heat,
formaldehyde,
formaldehyde,
chlorine,and
chlorine,and
ultraviolet
ultraviolet
light,
light,
2
2
%
%
iodine
iodine
and
and
oxidizing
oxidizing
agents
agents
(potassium
(potassium
permanganate)
permanganate)
·
·
Other
Other
enteroviruses,echoviruses,
enteroviruses,echoviruses,
and
and
coxsackieviruses
coxsackieviruses
has
has
been
been
reported
reported
to
to
cause
cause
an
an
illness
illness
simulating
simulating
paralytic
paralytic
poliomyelitis
poliomyelitis
.
.
·
·
The
The
most
most
frequent
frequent
cause
cause
of
of
(AFP)
(AFP)
that
that
must
must
be
be
distinguished
distinguished
from
from
polio
polio
is
is
Gullian-
Gullian-
Barre
Barre
syndrom(GBS).paralysis
syndrom(GBS).paralysis
of
of
polio
polio
is
is
usually
usually
asymmetric
asymmetric
,with
,with
fever
fever
present
present
at
at
onset
onset
,maximum
,maximum
extent
extent
of
of
paralysis
paralysis
is
is
usually
usually
reached
reached
within
within
(3-4
(3-4
days).
days).
·
·
Paralysis
Paralysis
in
in
(GBS)
(GBS)
is
is
typically
typically
symmetrical
symmetrical
,and
,and
may
may
progress
progress
as
as
long
long
as
as
10
10
days
days
with
with
sensory
sensory
changes
changes
seen
seen
in
in
the
the
majority
majority
of
of
GBS
GBS
cases
cases
.
.
Fever
Fever
,headache
,headache
,nausea
,nausea
,vomiting,
,vomiting,
characteristic
characteristic
of
of
polio
polio
are
are
absent
absent
in
in
GBS.
GBS.
·
·
Other
Other
causes
causes
of
of
AFB
AFB
include
include
transverse
transverse
myelitis
myelitis
,traumatic
,traumatic
neuritis,
neuritis,
toxic
toxic
neuropathies.
neuropathies.
·
·
The
The
virus
virus
enters
enters
through
through
the
the
mouth,
mouth,
and
and
primary
primary
multiplication
multiplication
of
of
the
the
virus
virus
occurs
occurs
at
at
the
the
site
site
of
of
implantation
implantation
in
in
the
the
pharynx
pharynx
and
and
gastrointestinal
gastrointestinal
tract.
tract.
The
The
virus
virus
is
is
usually
usually
present
present
in
in
the
the
throat
throat
and
and
in
in
the
the
stool
stool
before
before
the
the
onset
onset
of
of
illness.
illness.
One
One
week
week
after
after
onset
onset
there
there
is
is
less
less
virus
virus
in
in
the
the
throat,
throat,
but
but
virus
virus
continues
continues
to
to
be
be
excreted
excreted
in
in
the
the
stool
stool
for
for
several
several
weeks.
weeks.
The
The
virus
virus
invades
invades
local
local
lymphoid
lymphoid
tissue,
tissue,
enters
enters
the
the
bloodstream,
bloodstream,
and
and
then
then
may
may
infect
infect
cells
cells
of
of
the
the
central
central
nervous
nervous
system.
system.
Replication
Replication
of
of
poliovirus
poliovirus
causes
causes
the
the
typical
typical
manifestations
manifestations
of
of
poliomyelitis.
poliomyelitis.
Clinical
Clinical
features
features
·
·
The
The
incubation
incubation
period
period
for
for
poliomyelitis
poliomyelitis
is
is
commonly
commonly
6
6
to
to
20
20
days
days
with
with
a
a
range
range
of
of
3
3
to
to
35
35
days.
days.
·
·
the
the
response
response
to
to
poliovirus
poliovirus
infection
infection
is
is
highly
highly
variable
variable
and
and
has
has
been
been
categorized
categorized
on
on
the
the
basis
basis
of
of
the
the
severity
severity
of
of
clinical
clinical
presentation.
presentation.
·
·
Up
Up
to
to
95%
95%
of
of
all
all
polio
polio
infections
infections
are
are
inapparent
inapparent
or
or
asymptomatic.
asymptomatic.
Estimates
Estimates
of
of
the
the
ratio
ratio
of
of
in
in
apparent
apparent
to
to
paralytic
paralytic
illness
illness
(usually
(usually
200:1).
200:1).
Infected
Infected
persons
persons
without
without
symptoms
symptoms
shed
shed
virus
virus
in
in
the
the
stool
stool
and
and
are
are
able
able
to
to
transmit
transmit
the
the
virus
virus
to
to
others.
others.
·
·
Approximately
Approximately
4%
4%
–
–
8%
8%
of
of
polio
polio
infections
infections
consist
consist
of
of
a
a
minor,
minor,
nonspecific
nonspecific
illness
illness
without
without
clinical
clinical
or
or
laboratory
laboratory
evidence
evidence
of
of
central
central
nervous
nervous
system
system
invasion.
invasion.
This
This
clinical
clinical
presentation
presentation
is
is
known
known
as
as
abortive
abortive
poliomyelitis,
poliomyelitis,
and
and
is
is
characterized
characterized
by
by
complete
complete
recovery
recovery
in
in
less
less
than
than
a
a
week.
week.
Three
Three
syndromes
syndromes
observed
observed
with
with
this
this
form
form
of
of
poliovirus
poliovirus
infection
infection
are
are
upper
upper
respiratory
respiratory
tract
tract
infection
infection
(sore
(sore
throat
throat
and
and
fever),
fever),
gastrointestinal
gastrointestinal
disturbances
disturbances
(nausea,
(nausea,
vomiting,
vomiting,
abdominal
abdominal
pain,
pain,
constipation
constipation
or,
or,
rarely,
rarely,
diarrhea),
diarrhea),
and
and
influenza-like
influenza-like
illness.
illness.
These
These
syndromes
syndromes
are
are
indistinguishable
indistinguishable
from
from
other
other
viral
viral
illnesses.(minor
illnesses.(minor
illness).
illness).
Major
Major
illness
illness
·
·
It
It
is
is
characterized
characterized
by
by
involvement
involvement
of
of
the
the
nervous
nervous
system
system
and
and
may
may
be
be
one
one
of
of
the
the
following
following
two
two
type
type
·
·
1-
1-
aseptic
aseptic
meningitis
meningitis
it
it
is
is
seen
seen
in
in
1%
1%
of
of
all
all
infections
infections
.
.
The
The
presenting
presenting
features
features
include
include
stiffness
stiffness
and
and
pain
pain
in
in
the
the
neck
neck
and
and
back.
back.
·
·
2-
2-
paralytic
paralytic
polio
polio
(
(
less
less
than
than
1%)
1%)
:
:
classical
classical
presentation
presentation
depend
depend
on
on
site
site
of
of
involvement
involvement
(
(
spinal,
spinal,
bulbar
bulbar
and
and
bulbospinal,
bulbospinal,
encephalitic
encephalitic
form).
form).
·
·
The
The
fatality
fatality
rate
rate
of
of
paralytic
paralytic
cases
cases
is
is
2-10%.
2-10%.
·
·
Fewer
Fewer
than
than
1%
1%
of
of
all
all
polio
polio
infections
infections
result
result
in
in
flaccid
flaccid
paralysis
paralysis
,
,
the
the
majority
majority
of
of
it
it
result
result
in
in
non-
non-
specific
specific
fever
fever
·
·
(mild
(mild
illness
illness
with
with
headache,
headache,
malaise,
malaise,
nausea
nausea
and
and
vomiting
vomiting
),
),
and
and
this
this
may
may
progrss
progrss
into
into
major
major
illness
illness
(classical
(classical
flaccid
flaccid
paralysis)
paralysis)
·
·
Many
Many
persons
persons
with
with
paralytic
paralytic
poliomyelitis
poliomyelitis
recover
recover
completely
completely
and,
and,
in
in
most,
most,
muscle
muscle
function
function
returns
returns
to
to
some
some
degree.
degree.
Weakness
Weakness
or
or
paralysis
paralysis
still
still
present
present
12
12
months
months
after
after
onset
onset
is
is
usually
usually
permanent.
permanent.
·
·
Clusters
Clusters
of
of
susceptible
susceptible
persons
persons
including
including
groups
groups
that
that
refuse
refuse
immunization
immunization
,migrants
,migrants
,unregistered
,unregistered
children
children
,refugees
,refugees
are
are
at
at
high
high
risk.
risk.
·
·
Laboratory
Laboratory
diagnosis
diagnosis
·
·
Viral
Viral
isolation
isolation
·
·
Poliovirus
Poliovirus
may
may
be
be
recovered
recovered
from
from
the
the
stool
stool
or
or
pharynx
pharynx
of
of
a
a
person
person
with
with
poliomyelitis
poliomyelitis
.
.
Isolation
Isolation
of
of
virus
virus
from
from
the
the
cerebrospinal
cerebrospinal
fluid
fluid
(CSF)
(CSF)
is
is
diagnostic,
diagnostic,
but
but
is
is
rarely
rarely
accomplished.
accomplished.
Serology
Serology
·
·
Neutralizing
Neutralizing
antibodies
antibodies
appear
appear
early
early
and
and
may
may
be
be
at
at
high
high
levels
levels
by
by
the
the
time
time
the
the
patient
patient
is
is
hospitalized
hospitalized
·
·
Cerebrospinal
Cerebrospinal
fluid
fluid
In
In
poliovirus
poliovirus
infection,
infection,
the
the
CSF
CSF
usually
usually
contains
contains
an
an
increased
increased
number
number
of
of
white
white
blood
blood
cells
cells
(10
(10
–
–
200
200
cells/mm3,
cells/mm3,
primarily
primarily
lymphocytes)
lymphocytes)
and
and
a
a
mildly
mildly
elevated
elevated
protein
protein
(40
(40
–
–
50
50
mg/100
mg/100
ml).
ml).
Epidemiology
Epidemiology
Occurrence
Occurrence
·
·
Polio
Polio
occurred
occurred
worldwide
worldwide
sporadically
sporadically
and
and
as
as
epidemic
epidemic
usually
usually
in
in
area
area
of
of
low
low
sanitation
sanitation
and
and
low
low
vaccine
vaccine
coverage,
coverage,
few
few
cases
cases
of
of
vaccine
vaccine
polio
polio
occur
occur
every
every
year.
year.
Reservoir
Reservoir
·
·
Humans
Humans
are
are
the
the
only
only
known
known
reservoir
reservoir
of
of
poliovirus,
poliovirus,
which
which
is
is
transmitted
transmitted
most
most
frequently
frequently
by
by
persons
persons
with
with
inapparent
inapparent
infections.
infections.
Paralytic
Paralytic
patient
patient
as
as
well
well
as
as
mild,
mild,
missed,
missed,
and
and
inapparents
inapparents
cases
cases
discharge
discharge
the
the
virus
virus
in
in
oropharyngeal
oropharyngeal
secretion
secretion
and
and
stools.the
stools.the
virus
virus
is
is
demonstrated
demonstrated
in
in
the
the
throat
throat
as
as
early
early
as
as
36
36
hours
hours
after
after
infection
infection
and
and
persist
persist
for
for
about
about
1
1
week.in
week.in
faeces
faeces
demonstrated
demonstrated
within
within
72
72
hours
hours
after
after
infection
infection
and
and
persist
persist
for
for
3-6
3-6
weeks
weeks
or
or
longer
longer
.cases
.cases
are
are
most
most
infectious
infectious
during
during
the
the
first
first
few
few
days
days
following
following
infection
infection
.
.
Transmission
Transmission
·
·
Person-to-person
Person-to-person
spread
spread
of
of
poliovirus
poliovirus
via
via
the
the
fecal-oral
fecal-oral
route
route
is
is
the
the
most
most
important
important
route
route
of
of
transmission,
transmission,
it
it
occurs
occurs
through
through
close
close
contact.transmission
contact.transmission
by
by
pharangeal
pharangeal
rout
rout
(droplet
(droplet
infection
infection
)is
)is
less
less
common
common
but
but
it
it
is
is
more
more
important
important
during
during
epidemics
epidemics
.
.
Temporal
Temporal
pattern
pattern
·
·
Poliovirus
Poliovirus
infection
infection
typically
typically
peaks
peaks
in
in
the
the
summer
summer
months
months
in
in
temperate
temperate
climates.
climates.
There
There
is
is
no
no
seasonal
seasonal
pattern
pattern
in
in
tropical
tropical
climates.
climates.
·
·
Communicability
Communicability
·
·
Poliovirus
Poliovirus
is
is
highly
highly
infectious,
infectious,
with
with
seroconversion
seroconversion
rates
rates
among
among
susceptible
susceptible
household
household
contacts
contacts
of
of
children
children
nearly
nearly
100%,
100%,
and
and
greater
greater
than
than
90%
90%
among
among
susceptible
susceptible
household
household
contacts
contacts
of
of
adults.
adults.
Persons
Persons
infected
infected
with
with
poliovirus
poliovirus
are
are
most
most
infectious
infectious
from
from
7
7
to
to
10
10
days
days
before
before
and
and
after
after
the
the
onset
onset
of
of
symptoms,
symptoms,
but
but
poliovirus
poliovirus
may
may
be
be
present
present
in
in
the
the
stool
stool
from
from
3
3
to
to
6
6
weeks.
weeks.
Susceptibility
Susceptibility
and
and
resistance
resistance
·
·
In
In
tropical
tropical
countries
countries
,
,
polio
polio
still
still
a
a
disease
disease
of
of
childhood
childhood
most
most
cases
cases
occurring
occurring
under
under
5
5
years
years
of
of
age
age
.
.
·
·
Infants
Infants
up
up
to
to
6
6
months
months
are
are
immune
immune
because
because
of
of
maternal
maternal
antibodies
antibodies
.
.
·
·
Incidence
Incidence
is
is
highest
highest
in
in
(6
(6
months
months
-3
-3
years
years
).
).
·
·
It
It
is
is
rare
rare
after
after
5
5
years
years
·
·
In
In
countries
countries
with
with
better
better
sanitation
sanitation
,
,
the
the
age
age
incidence
incidence
is
is
rising
rising
and
and
the
the
total
total
incidence
incidence
is
is
falling
falling
because
because
of
of
regular
regular
immunization
immunization
.
.
·
·
Muscular
Muscular
fatigue
fatigue
,chills,
,chills,
IM
IM
injection
injection
to
to
person
person
freshly
freshly
infected,
infected,
pregnancy
pregnancy
predispose
predispose
to
to
developments
developments
of
of
paralytic
paralytic
polio.
polio.
·
·
Immunity
Immunity
produced
produced
by
by
natural
natural
infection
infection
is
is
type
type
specific
specific
and
and
long
long
lasting
lasting
.
.
·
·
Second
Second
attack
attack
are
are
rare
rare
and
and
are
are
attributable
attributable
to
to
infection
infection
by
by
different
different
strain.
strain.
Prevention
Prevention
and
and
control
control
·
·
The
The
salk
salk
vaccine
vaccine
,introduced
,introduced
in
in
1954,
1954,
is
is
an
an
inactivated
inactivated
polio
polio
vaccine
vaccine
(IPV)
(IPV)
administrated
administrated
parenterally
parenterally
.
.
·
·
The
The
sabin
sabin
vaccine
vaccine
,
,
introduced
introduced
in
in
1961
1961
,
,
is
is
a
a
live
live
attenuated
attenuated
oral
oral
vaccine
vaccine
(OPV)
(OPV)
given
given
orally.
orally.
·
·
The
The
WHO
WHO
recommends
recommends
the
the
OPV
OPV
because
because
of
of
the
the
following
following
advantages:
advantages:
o
o
It
It
is
is
more
more
effective
effective
in
in
stopping
stopping
the
the
spread
spread
of
of
wild
wild
polioviruses.
polioviruses.
It
It
multiplies
multiplies
and
and
stimulates
stimulates
immunity
immunity
in
in
the
the
intestine
intestine
by
by
inhibiting
inhibiting
the
the
growth
growth
of
of
wild
wild
strain
strain
and
and
its
its
transmission
transmission
to
to
others.
others.
o
o
It
It
is
is
easier
easier
to
to
administer.
administer.
o
o
Cheaper.
Cheaper.
o
o
It
It
Provides
Provides
longer
longer
immunity
immunity
at
at
least
least
for
for
3
3
years
years
.
.
o
o
It
It
is
is
useful
useful
in
in
control
control
of
of
epidemic
epidemic
s.
s.
o
o
OPV
OPV
is
is
excreted
excreted
in
in
stools
stools
for
for
4-6
4-6
weeks
weeks
after
after
a
a
dose
dose
is
is
administered
administered
.the
.the
contact
contact
of
of
the
the
person
person
immunized
immunized
and
and
thus
thus
develop
develop
immunity
immunity
Control
Control
·
·
1.
1.
report
report
to
to
local
local
heath
heath
authority.
authority.
·
·
2.
2.
isolation
isolation
and
and
enteric
enteric
precaution
precaution
.
.
·
·
3.
3.
protection
protection
of
of
contacts
contacts
and
and
source
source
of
of
infection
infection
:
:
signal
signal
case
case
of
of
polio
polio
due
due
to
to
wild
wild
polio
polio
virus
virus
in
in
a
a
country
country
is
is
a
a
public
public
health
health
emergency
emergency
and
and
so
so
planning
planning
for
for
large
large
scale
scale
response
response
searching
searching
for
for
additional
additional
cases
cases
of
of
AFP.
AFP.
·
·
4.
4.
specific
specific
treatments
treatments
:
:
physical
physical
therapy
therapy
is
is
used
used
to
to
attain
attain
maximum
maximum
function
function
after
after
paralytic
paralytic
polio.
polio.
The
The
strategies
strategies
to
to
achieve
achieve
polio
polio
eradication
eradication
are:
are:
·
·
Attaining
Attaining
high
high
routine
routine
coverage
coverage
(>90%)with
(>90%)with
at
at
least
least
three
three
doses
doses
of
of
oral
oral
polio
polio
vaccine
vaccine
within
within
first
first
year
year
of
of
life.
life.
·
·
Conducting
Conducting
National
National
Immunization
Immunization
Days.(NIDs)
Days.(NIDs)
·
·
Conducting
Conducting
Mopping
Mopping
up
up
immunization
immunization
.
.
·
·
Surveillance
Surveillance
for
for
all
all
possible
possible
cases
cases
of
of
polio.(AFP).
polio.(AFP).
Contraindication
Contraindication
·
·
1-
1-
immunodeficiency
immunodeficiency
state
state
.siblings
.siblings
of
of
an
an
immunodeficiency
immunodeficiency
individual
individual
should
should
not
not
be
be
given
given
an
an
OPV
OPV
.
.
Such
Such
individual
individual
given
given
IPV.
IPV.
··
··
2-
2-
Severe
Severe
allergic
allergic
reaction
reaction
to
to
a
a
vaccine
vaccine
component
component
or
or
following
following
a
a
prior
prior
dose
dose
of
of
vaccine
vaccine
··
··
3-
3-
Moderate
Moderate
or
or
severe
severe
acute
acute
illness.
illness.
·
·
Diarrhea
Diarrhea
is
is
not
not
a
a
contraindication
contraindication
,but
,but
the
the
dose
dose
should
should
not
not
be
be
be
be
counted
counted
and
and
another
another
dose
dose
should
should
be
be
given
given
at
at
the
the
first
first
opportunity(
opportunity(
this
this
is
is
because
because
the
the
virus
virus
unable
unable
to
to
establish
establish
itself
itself
in
in
the
the
intestine
intestine
due
due
to
to
diarrhrea
diarrhrea
).
).
Immunization
Immunization
of
of
adult
adult
·
·
Non
Non
immunized
immunized
adult
adult
travelling
travelling
to
to
endemic
endemic
area
area
.
.
·
·
Laboratory
Laboratory
workers
workers
handling
handling
specimens
specimens
containing
containing
poliovirus
poliovirus
.
.
·
·
Health
Health
care
care
workers
workers
who
who
may
may
be
be
exposed
exposed
to
to
patients
patients
excreting
excreting
wild
wild
type
type
poliovirus.
poliovirus.
Epidemiologicl
Epidemiologicl
basis
basis
for
for
polio
polio
eradication
eradication
·
·
Poliomyelitis
Poliomyelitis
is
is
eradicable
eradicable
because:
because:
·
·
Man
Man
is
is
the
the
only
only
host
host
.
.
·
·
Long
Long
term
term
carrier
carrier
state
state
is
is
not
not
known
known
to
to
occur.
occur.
·
·
The
The
half
half
life
life
of
of
excreted
excreted
virus
virus
in
in
the
the
sewage
sewage
is
is
about
about
48
48
hours
hours
and
and
spread
spread
can
can
only
only
occur
occur
during
during
this
this
period
period
.
.
·
·
OPV
OPV
is
is
easy
easy
to
to
administer
administer
and
and
dose
dose
not
not
need
need
highly
highly
trained
trained
personnel
personnel
.
.
·
·
OPV
OPV
is
is
cheap.
cheap.
·
·
OPV
OPV
live
live
vaccine
vaccine
multiplies
multiplies
in
in
the
the
intestine
intestine
and
and
can
can
interrupt
interrupt
the
the
transmission
transmission
of
of
wild
wild
poliovirus
poliovirus
.(the
.(the
vaccine
vaccine
virus
virus
mimics
mimics
the
the
natural
natural
route
route
of
of
infection
infection
,
,
and
and
can
can
be
be
transmitted
transmitted
from
from
a
a
recently
recently
vaccinated
vaccinated
child
child
to
to
close
close
contacts
contacts
who
who
have
have
not
not
vaccinated
vaccinated
.herd
.herd
immunity
immunity
is
is
achieved
achieved
in
in
case
case
of
of
polio
polio
if
if
two
two
third
third
of
of
community
community
is
is
immunized).
immunized).
What
What
Would
Would
Happen
Happen
If
If
We
We
Stopped
Stopped
Vaccinations?
Vaccinations?
·
·
Most
Most
vaccine-preventable
vaccine-preventable
diseases
diseases
are
are
spread
spread
from
from
person
person
to
to
person.
person.
If
If
one
one
person
person
in
in
a
a
community
community
gets
gets
an
an
infectious
infectious
disease,
disease,
he
he
can
can
spread
spread
it
it
to
to
others
others
who
who
are
are
not
not
immune.
immune.
But
But
a
a
person
person
who
who
is
is
immune
immune
to
to
a
a
disease
disease
because
because
she
she
has
has
been
been
vaccinated
vaccinated
can
can
’
’
t
t
get
get
that
that
disease
disease
and
and
can
can
’
’
t
t
spread
spread
it
it
to
to
others.
others.
The
The
more
more
people
people
who
who
are
are
vaccinated,
vaccinated,
the
the
fewer
fewer
opportunities
opportunities
a
a
disease
disease
has
has
to
to
spread.
spread.
·
·
If
If
one
one
or
or
two
two
cases
cases
of
of
disease
disease
are
are
introduced
introduced
into
into
a
a
community
community
where
where
most
most
people
people
are
are
not
not
vaccinated,
vaccinated,
outbreaks
outbreaks
will
will
occur.
occur.
Making
Making
Progress
Progress
Toward
Toward
a
a
World
World
Without
Without
Polio
Polio
·
·
A
A
world
world
free
free
from
from
polio
polio
is
is
possible
possible
thanks
thanks
to
to
extraordinary
extraordinary
progress
progress
mades
mades
by
by
the
the
Global
Global
Polio
Polio
Eradication
Eradication
Initiative
Initiative
in
in
1988
1988
when
when
350,000
350,000
polio
polio
cases
cases
were
were
reported
reported
in
in
125
125
polio-endemic
polio-endemic
countries
countries
around
around
the
the
world.
world.
By
By
2001,
2001,
those
those
numbers
numbers
were
were
reduced
reduced
to
to
475
475
cases
cases
in
in
only
only
10
10
polio-endemic
polio-endemic
countries,
countries,
and
and
today
today
wild
wild
polio
polio
virus
virus
remains
remains
endemic
endemic
in
in
just
just
three
three
countries
countries
—
—
Afghanistan,
Afghanistan,
Nigeria,
Nigeria,
and
and
Pakistan.
Pakistan.
·
·
Today
Today
80%
80%
of
of
the
the
world
world
’
’
s
s
people
people
now
now
live
live
in
in
polio-free
polio-free
area.
area.
So
So
far
far
in
in
2014,
2014,
as
as
of
of
8
8
October,
October,
only
only
222
222
cases
cases
have
have
been
been
reported
reported
worldwide.
worldwide.
Of
Of
these,
these,
84%
84%
are
are
from
from
Pakistan.
Pakistan.