The document discusses poliomyelitis (polio), including: - Polio is an acute viral infection caused by poliovirus that can cause paralysis. It is transmitted through the fecal-oral route or droplets. - There are three types of poliovirus. Infection results in subclinical, abortive, non-paralytic, or paralytic cases. Paralysis occurs when the virus infects motor neurons in the spinal cord. - Pakistan saw over 1,000 polio cases in 1997 but improved vaccination programs have reduced this to single digits by 2022. Oral and inactivated polio vaccines are used to prevent transmission and eradicate the disease.

1. WHAT IS POLIO?
Epidemiological Studies
GROUP : 01
BS MICROBIOLOGY-
4TH SEMESTER
MIC-408 DEPARTMENT OF
MICROBIOLOGY

2. CONTENTS
1- History Of Polio
2- Introduction
• What Is Polio?
• Different Types Of Polio
• Etiology
• Risk Factors
3- Mode Of Transmission
• Infectious Material
• How does it Transmit?
• Incubation Period Of Virus
4- Pathogenesis
5- Clinical Features
• Abortive Infection
• Paralytic Polio
• Non-paralytic Polio
6- Diagnosis
7- Treatment And Prevention
8- Epidemiology In Pakistan
9- Strategies
10- Conclusion
11- References

3. HISTORY
Poliomyelitis
• First described by Michael
• Underwood in 1789
• Developed countries in
• Northern Hemisphere
suffered increasingly severe
• epidemics in the first half
of the 20th century
• More than 21,000 paralytic
• cases reported in the U.S.
in 1952
• Last case of wild poliovirus
• acquired in the U.S. was 1979
• 1147 cases were reported in Pakistan in
in 1997

4. INTRODUCTION
What is polio?
• Poliomyelitis is an acute viral infection caused by an RNA virus.
• The term “Poliomyelitis” derives from the ancient Greek word
Polio’s means “grey” and myelos meaning “marrow” referring to
the grey matter of the spinal cord. The suffix itis denotes
inflammation, i.e. inflammation of the spinal cord’s grey matter.

5. DIFFERENT TYPES
1) Spinal Polio: It is the most common form
characterized by asymmetric paralysis that most often
involves the legs. 79% of paralytic cases
2) Bulbar Polio: This leads to weakness of muscles
innervated by cranial nerves. approximately 2% of
paralytic cases
3) Bulbospinal Polio: It is a combination of bulbar and
spinal paralysis approximately 19% of paralytic cases
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 degrees of paralysis, and possible death

6. ETIOLOGY
• The causative agent is the poliovirus which has three
serotypes 1,2, and 3.
• Most outbreaks of paralytic polio are due to the type 1
virus.
• Poliovirus is a member of the enterovirus subgroup,
family Picornaviridae.
• Picornaviruses are small, ether-insensitive
viruses with an RNA genome.
• Poliovirus can survive for long periods in
the external environment.
• In a cold environment, it can live in water for
4 months and in feces for 6 months.

7. REPLICATION CYCLE OF
POLIO VIRUS

8. Risk Factors
Environmental Factors
 Polio is likely to occur during the rainy season.
 The environmental sources of infection are contaminated
water, food, and flies.
 Poliovirus survives for a long time in a cold environment.
 Overcrowding and poor sanitation provide opportunities
for exposure to infection.
Host Factors
Age: The disease occurs in all age groups, but children are
more susceptible.
 • In Pakistan polio is essentially a disease of infancy and
childhood
• Gender: The ratio of male to female is 3:1

9. TRANSMISSION
Infectious Material • The virus is found in the feces and oropharyngeal secretions of an
infected person.
Mode Of Transmission
1. Fecal-oral Route
2. Droplet Infection
FECAL-ORAL ROUTE
• This is the main route of transmission in developing countries.
• 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.
DROPLET INFECTION
• This may occur during the acute phase of the disease when the virus occurs in the throat.
• Close personal contact with an infected person facilitates droplet spread.
• This mode of transmission may be relatively more important in developed countries.

11. INCUBATION PERIOD OF VIRUS
 7-14 days
 Estimated to be about 2 weeks
 The virus is excreted commonly for 2 to 3 weeks, sometimes as long as
3 to 4 months in feces.
 In polio cases, infectivity in the pharyngeal foci is around one week,
and in the intestinal foci 6-8 weeks
PERIOD OF COMMUNICABILITY
RESERVOIR
 Humans are the only known reservoir of poliovirus
CASE FATILITY
 it varies from 1-10% according to form of disease (higher in
bulbar), complications and age

12. PATHOGENESIS
• The virus enters through the mouth and multiplies
in the oropharynx and gastrointestinal tract.
• The virus is usually present in nasopharyngeal
secretions for 1 to 2 weeks and can be shed in
stools for several weeks after infection, even in
individuals with minor symptoms or no illness.
• During intestinal replication, the virus invades local
lymphoid tissue and may enter the bloodstream, and
then infect cells of the central nervous system.
• Poliovirus-induced destruction of motor neurons of
the anterior horn of the spinal cord and brain stem
cells results in distinctive paralysis.

14. CLINICAL SPECTRUM
Four basic patterns of Polio infections are as follows:-
• Subclinical infections
• Abortive infection
• Paralytic infection
• Non-paralytic infection
Inapparent (Subclinical) Infection
• This occurs approximately in 91 to 96% of poliovirus infections.
• There are no presenting symptoms and recognition is done only
by virus isolation.
Abortive Polio
• Is also called a minor illness.
• Occurs approximately 4 to 8 % of the infections.
• This is one of the earliest stages and most cases do not progress
further.
• At this stage the virus is beginning to infect cells and spread to
the lymphatic system.
• It includes symptoms like- General discomfort or
uneasiness(malaise), headache, red throat, slight fever, sore
throat, vomiting etc

15. NON PARALYTIC POLIO
• Occurs in approximately 1% of all infections.
• This stage is not common but occurs when the virus is not
destroyed by antibodies and spreads to the CNS.
• The presenting features are stiffness and pain in the neck and
back.
• The disease lasts for 2 to 10 days.
• The disease is synonymous with septic meningitis.
PARALYTIC POLIO
• It includes the development of flaccid paralysis (AFP) and affects
the central nervous system.
• Occurs in less than 1% of infections.
• The other associated symptoms are malaise, anorexia, nausea,
vomiting, constipation, and abdominal pain.
Cont.……..

16. • There might be signs of meningeal irritation, i.e., stiffness of neck and back muscles.
• The child finds difficulty in sitting and sits by supporting hands at the back and by
partially flexing the hips and knees.
• Paralysis is characterized as descending.
• e.g., starting at the hip and then moving down to the distal parts of the extremity.
• Progression of paralysis to reach its maximum in the majority of cases occurs in less than
4 days
• No sign of sensory loss.
Cont.…….

17. Complications and case fatality
 Respiratory complications: pneumonia, pulmonary edema
 Cardiovascular complications: myocarditis
 Late complications: soft tissue and bone deformities,
osteoporosis, and chronic distension of the colon.
 Case fatality: varies from 1% to 10% according to the form of
the disease (higher in bulbar), complications, and age ( fatality
increases with age).

18. DIAGNOSIS
The health care provider may find:-
• Abnormal reflexes, Back stiffness, Difficulty in movement
Tests include
• Cultures of throat washing, stools or spinal fluid, spinal tap, and
examination of the spinal fluid (CSF exam.) using PCR.
Virus isolation
The likelihood of poliovirus isolation is
• Highest from stool specimens,
• Intermediate from pharyngeal swabs
• Very low from blood or spinal fluid.

19. TREATMENT
The goal of the treatment is to control symptoms
as there is no specific treatment for this viral
infection.
Symptoms are treated based on their severity.
Treatment may include-
• Antibiotics for urinary tract infection
• Moist heat to reduce pain and spasms
• Pain killers to reduce headache, muscle pain,
and spasms
• Physical therapy or orthopedic surgery are also
provided to help in recovering muscle strength
and function

20. PREVENTION
Polio immunization(vaccine) effectively prevents poliomyelitis.
There are mainly two types of vaccines that are widely used to prevent
poliomyelitis.
1. Inactivated (Salk) Polio Vaccine (IPV)
Dr. Jonas Salk In 1953
• It is given as an injection in the leg or arm, depending on the patient’s age
at the angle of 45ºC
• Don’t inject it on the buttock because there are chances of abscess
formation.
• Prevents paralysis
• IPV is administered by subcutaneous injection with having 0.5ml syringe
and needle of number 24.
• The First dose is administered when the infant is 14 weeks old with OPV
3rd dose and 2nd is given when the infant is 9 months old.
• Induces humoral antibodies but not local immunity
• Protect the individual but do not prevent reinfection.

21. Oral (Sabin) Polio Vaccine (OPV)
4-types (mOPV, nOPV2, bOPV, tOPV)
Dr. Albert Sabin in 1957
• It contains a live attenuated virus (types 1,2, and 3, trivalent)
grown in primary monkey kidney or human diploid cell cultures.
• Shed in feces hence protect also surroundings.
• Zero doses to children delivered in hospitals.
• The first dose is administered when the infant is 6 weeks old.
The 2nd dose is when the infant is 10 weeks old and the third is
when the infant is 14 weeks old
• Vaccines type Bivalent OPV for serotype 1 and 3 and
Monovalent OPV for serotype 3 only are in use in Pakistan.
• It produces antibodies in the blood to all three types of
poliovirus.
• Prevents not only paralysis but also intestinal re-infection.
Cont…..
Case exception*: if the child is suffering from diarrhea, then the vaccine will not work
well, then give another dose after 4-weeks when the course is over.

22. Difference Between IPV And OPV

23. Epidemiological distribution of polio in Pakistan
• Pakistan is one of three remaining polio-
endemic countries in the world, along with
Afghanistan and Nigeria
• Since the launch of Pakistan’s Polio
Eradication Programme in 1974 which
started work officially in 1994, there has
been a massive decline in polio cases in
Pakistan from approximately 20,000 every
year in the early 1990s to only few cases in
2022

26. 1147
341
558
199
119
90 103
53
28 40 32
117
89
144
198
74
141
328
54
20 8 12
147
84
1 6
0
200
400
600
800
1000
1200
1400
1600
1800
2000
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022
Years
Polio
cases
Polio cases in Pakistan 1997-NOW

27. Strategies to Control Polio In Pakistan
• Pakistan has made important progress toward
stopping poliovirus transmission in the country
.
• Since 1994, the Pakistan Polio Eradication
Program me has been fighting officially to
end the crippling poliovirus from the country.

28. • Throughout the year, the program implements high-quality vaccination
campaigns (containing almost 339,521 trained workers) that aim to
reach all children under the age of across Pakistan.
• The program is currently implementing the National Emergency
Action Plan (NEAP) for Polio Eradication.
• The program is committed to stopping all wild poliovirus type 1
(WPV1) and vaccine-derived poliovirus type 2 (VDPV2)
transmission in Pakistan.
Cont.…….
In 2008, The government of Pakistan
introduce the pentavalent vaccine which is a
combination of 5 vaccines (DPT-HepB-Hib)
In 2012 pneumococcal and in august 2015
IPV was introduced in Pakistan.

29. To achieve this goal, the program is focused on ensuring the
following objectives:
• Special attention to children who have the least access to
polio drops during the campaign.
• Acknowledging the basic importance of vaccines in the
polio program and highlighting its services in front of the
public.
• Taking steps on a war basis by adding the sensitive areas of
Polio to the priority-1.
• The establishment of the health camp, where EPI is also
informed with polio drops.
• Involvement and training of women volunteers in a
community-based vaccination program.
• Very good monitoring management.
Cont.….

30. IMMUNIZATION
RECORD KEEPING

31. cVDPV2 type
polio cases
Wild type
polio cases

32. CONCLUSION
1. Poliomyelitis is an acute enteroviral illness.
2. The most devastating result of poliovirus infection is ‘paralysis’.
3. This disease results in the destruction of motor neurons caused by
the polio virus
4. Vaccination is the only effective method of prevention.
World Polio Day
24 OCTOBER

33. REFRENCES
 A Textbook of Microbiology by R. Ananthanarayan, C K Jayaram
Paniker, seventh edition, 2005, Page no: 491-494.
 A Textbook of Microbiology by P. Chakraborty, 3rd edition, 2013, Page
No: 555-559.
 https://www.unicef.org/pakistan/polioww
 Pakistan Polio Update: http://endpolio.com.pk/media-room/pakistan-
polio-update

34. Why There Is a Permanent Disability In
Polio?