Seminar on Epidemiology of poliomyelitis and strategy for eradication. Ref : K. Park

1. By Sanjay George
EPIDEMIOLOGY OF POLIOMYELITIS
AND STRATEGY FOR ERADICATION

2. INTRODUCTION
• Pre-vaccination era : Polio was worldwide
• 1988 : World Health Assembly resolved to eradicate Polio
• 1988 : 125 endemic countries
• 2008 : 4 endemic countries – India, Pakistan, Afghanistan
and Nigeria
• Last reported case in India was 0n 13th January 2011.

3. CAUSATIVE AGENT
• Poliovirus – Enterovirus (RNA virus) belonging to Picornaviridae
• Serotypes – 1,2,3 (most outbreaks due to type-1)
• Mode of Transmission – Feco-oral Route & Droplet Infection
• Reservoir of Infection – Man
• Infectious Material – Feces and oro-pharyngeal secretion of infected
person.
• Period of Communicability – 7 to 10 days before and after onset of
symptoms. In feces virus excreted for 2 to 3 weeks sometimes as
long as 3 to 4 months.
• Incubation Period – 7 to 14 days.

4. HOST FACTORS
• Age: Children most susceptible. 6months to
3years most vulnerable
• Sex
• Risk Factors
• Immunity

5. ENVIRONMENTAL FACTORS
• More common during rainy season
• Environmental Sources – Contaminated
food, water and flies
• Overcrowding and poor sanitation contribute to
spread of infection.

6. CLINICAL SPECTRUM
• Unapparent (Subclinical) Infection : 91 – 96%
• Abortive Polio or Minor Illness : 4 – 8%
• Non-Paralytic Polio : 1%
• Paralytic Polio : Less than 1%

7. PARALYTIC POLIO
• Less than 1% of infections.
• Virus invades CNS causing various degrees of paralysis
• Asymmetrical flaccid paralysis
• H/O fever at time of onset of paralysis indicative of Polio
• Malaise, anorexia, vomiting, headache, sore
throat, constipation, abdominal pain
• Signs of meningeal irritation
• Tripod Sign may be present

9. PARALYTIC POLIO CONTD.
• Descending paralysis
• No sensory loss
• Cranial nerves maybe involved
• There maybe facial asymmetry, difficulty in
swallowing, weakness or loss of voice.
• Respiratory insufficiency can lead to death

10. PREVENTION
• Immunization is the sole effective method to
control Polio.
• 2 types of vaccines are available:
• - Inactivated (Salk) polio vaccine
• - Oral (Sabin) polio vaccine

11. IPV
• Vaccine contains 40 units of type -1 antigen. 8 units of type – 2 and 32
units of type – 3 D antigen.
• IM route
• 1st 3 doses given at interval of 1 - 2 months and fourth dose 6 – 12
months after the third dose.
• First dose : 6 weeks
• Drawback:
• No benefit to community
• Immunity not rapidly achieved
• Shouldn’t be administered during epidemic
• Advantages
• Safer vaccine

12. OPV
• Live attenuated vaccine, Trivalent vaccine
• Contains 3,00,00 TCID 50 of type 1 poliovirus, 1,00,000
TCID 50 of type 2 virus and over 3,00,00 TCID 50 of type 3
virus.
• Dose : 2 drops
• National Immunization Programme : recommends
primary course of 3 doses at 1 month intervals
• First dose at 6 weeks.

13. EPIDEMIOLOGICAL INVESTIGATIONS
• Immediate epidemiological investigation.
• Epidemic: 2 or more local cases caused by the same virus
type in a 4 week period.
• Feces samples forwarded to lab
• Paired sera should be collected.
• WHO should be notified
• Within epidemic area OPV should be provide for all
persons over 6 weeks of age who have not been
previously immunized or immune status is unknown.

14. STRATEGIES FOR ERADICATION IN
INDIA
• Pulse Polio Immunization Days
• High levels of immunization coverage
• Monitor OPV coverage at district level and below
• Improved surveillance capable of detecting all cases of
AFP
• Rapid case investigation
• Arrange follow up at 60 days
• Conduct outbreak control for confirmed or suspected
cases

15. LINE LISTING OF CASES
• Started in 1989 to check for duplication, year of onset of
illness, identification of high risk pocket groups and documentation
of high risk age groups
• All cases of AFP should be reported to chief medical officer/district
immunization officer with following details
• Name, age and sex of patient
• - Father’s name and complete address
• - Vaccination Status
• - Date of onset of paralysis and date of reporting
• - Clinical Diagnosis
• - Doctor’s name, address and phone number

16. MOPPING UP
• Last stage in polio eradication
• Involves door to door immunization in high risk
districts where wild polio virus is present.

17. PULSE POLIO IMMUNIZATION
• Refers to sudden, simultaneous, mass administration of OPV
on a single day to all children 0 – 5 years of age regardless of
prior immunization status.
• It occurs as 2 rounds about 4 – 6 weeks apart during low
transmission season of Polio, i.e.. Between November –
February
• Doses of OPV in PPIs are extra doses
• Children should receive scheduled doses as well as PPI doses.
• No minimum interval between scheduled dose and PPI dose
• Vaccines use vial monitors

19. AFP SURVEILLANCE
• PPI supported by AFP surveillance
• Conducted by network of surveillance medical officers
• SMOs are located at state HQs and regional places in case
of larger states.
• Regular weekly reporting system

20. WHO STRATEGIES
• Global Polio Eradication Initiative
• - Use of Bivalent OPVs
• - State/district/block specific plans for endemic and re-
established transmission areas
• - Special teams and tactics for under served population
like highly migrant laborers
• - Short Interval Additional Dose
• - Monitoring of SIA coverage
• - Expanded environmental sampling

21. WHO STRATEGIES CONTD.
• - Serological surveys to document program status, assess
prospects and adjust plans accordingly by more
accurately determining population immunity.
• - Enhanced AFP surveillance
• - Enhance communication/social mobilization in priority
areas
• - Rehabilitation of Polio affected individuals