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.)