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EPIDEMIOLOGY&CONTROL
OF
POLIOMYELITIS
BY
DR. AWATIF ALAM
POLIOMYELITIS
(Polioviral fever, Infantile Paralysis)
Identification:
An acute viral infection, ranging from:
- Inappropriate infection,
- non-paralytic febrile illness ,
- aseptic meningitis ,
- paralytic disease ,
- possible death.
CLINICAL PICTURE:Fever,
malaise,
headaches ,
nausea and vomiting,
ms. pain and spasms and
stiff neck and back with or without
flaccid paralysis
(Hall Mark of poliomyelitis)
Viremia
Invasion of the CNS and selective
involvement of motor cells result in
flaccid paralysis .
(most commonly of lower extremities
and is characteristically
asymmetrical
Note:
Disease may occur in one of
3 forms:-
Inapparant infection =
minor illness in 90-95% of
cases.
Abortive illness: a mild,
flu-like, self limiting illness,
in 4-8% of cases.
Paralytic polio in, 1-2% of
cases.*
Incubation Period:- Commonly 7-14 days for paralytic cases,
(with a range of 3 to possibly 35 days.)
Agent:
Serotypes: three types referred to as
1= most paralytogenic
2 =Least virulent & uncommon
3 = Less frequent
- The virus is fairly stable and can survive for
long periods outside the host
(e.g. in water, milk or food)
- It is also resistant to acid and bile
(i.e. fully adapted to GIT).
Reservoir: Man (virus multiply in GIT &
excreted in faeces).
Mode of transmission:
1- “Faecal – oral” is the major route
(where sanitation Is deficient + poor water
supply & overcrowding is evident).
2- Person-to-person, i.e. direct spread (via
faecally contam. fingers or eating utensils).
3- Respiratory droplets route ≈ less imp.
Period of Comm.: “ Not accurately known.”
Cases are probably most infectious during the
first few days before and after onset of
symptoms”.
Susceptibility with Resistance:- Susc. is general, but paralytic infection
is rare , increasing in frequency with
age at time of infection.*
- Solid, type specific resistance
follows both clinically recognizable and
inapparent infection.
- Secondary attacks are rare.
- Infants posses transient passive
immunity to paralysis.
* An increased suscep. to paralytic
polio is associated with pregnancy.
Occurrence
- Geography: Worldwide
- Age:
Children < 3 yrs.
Highest mortality among infants.
-
Sex: No difference.
- Seasonality:- The disease is
endemic in tropics, outbreaks occur in
late summer and early autum.
METHODS OF CONTROL
Preventive Measures:Currently available vaccines are :
A. IPV
(salk – killed)
B. OPV
(sabin – live attenuated)
OPV is preferred in most countries :
- Less expensive and easily administered,
- Induces both circulating antibodies and
intestinal resistance
- And protects susceptible contacts by
secondary spread.
IPV:
More expensive
Harder to administer, but safer
and stable.
Requires wide vaccine coverage
WHO currently recommends OPV for
routine use in EPI.
Public education on advantages of
vaccination in early childhood, with
information on modes of spread.
Control of pt., contacts &immediate
environment:
1.Report to L.H.A.: Obligatory case
report of paralytic cases as a disease
under surveillance by WHO.
2. Isolation: Enteric precautions in
hospitals.
( under home conditions :
of little value due to risk of spread
of infection during prodromal period).
3. Concurrent disinfection: of throat
discharges, faeces and soiled
articles.
4.Quarantine:- No ? because of
large nos. of unrecognised
infections in the population.
?5.Protection Of Contacts:
Vaccination of little help.
6.Investigation of contacts: Search
for sick persons esp. children (to
assure early detection and to facilitate
Rx of unrecognised & unreported
cases)..
X7.Specific Rx:
None; supportive measures:
- analgesics,
- fluid Intake,
- avoid deformities &
- learning compensatory skills.
Note:
“Post-polio syndrome” :
Foot drop,
scoliosis &
other deformities leading to
functional impairment (may be late
manifestations of initially mild or
inappropriate illness.)