Poliovirus is an enterovirus that causes the disease poliomyelitis. It has a positive-sense RNA genome and protein capsid. Poliovirus infects human cells by binding to the poliovirus receptor on the cell surface and is then taken up by endocytosis. The virus can invade the brain and spinal cord, causing paralysis. While most poliovirus infections cause no symptoms, it can also cause flu-like symptoms or meningitis. There are currently two vaccines that can prevent polio.

2. • Poliovirus, the causative agent of
poliomyelitis (commonly known as
polio), is a human enterovirus and
member of the family of
Picornaviridae.
• Poliovirus is composed of an
RNAgenome and a protein capsid.
• The genome is a single-
stranded positive-sense RNA
Virus genome that is about
7500 nucleotides long.
• The viral particle is about 30
nm in diameter with
icosahedral symmetry.

3. • Because of its short genome and
its simple composition—only RNA
and a nonenveloped icosahedral
protein coat that encapsulates it,
poliovirus is widely regarded as
the simplest significant virus.
• Poliovirus was first isolated in
1909 by Karl Landsteiner and
Erwin Popper.
• Poliovirus infects human cells by
binding to an immunoglobulin-like
receptor, poliovirus receptor (PVR))
on the cell surface.
• Interaction of poliovirus and PVR
facilitates an irreversible
conformational change of the viral
particle necessary for viral entry.

4. • The virus spreads from person to
person and can invade an infected
person’s brain and spinal cord,
causing paralysis (can’t move parts
of the body).
• The virus enters through the mouth
and multiplies in the throat and
gastrointestinal tract;
• Then moves into the bloodstream
and is carried to the central
nervous system where it replicates
and destroys the Motor Neuron
Cells.
• Motor neurons control the muscles
for swallowing, circulation,
respiration, and the trunk, arms,
and legs.

5. Poliovirus bound to a neuron receptor

6. • Attached to the host cell membrane,
entry of the viral nucleic acid was
thought to occur one of two ways:
a.) Via the formation of a pore in the
plasma membrane through which
the RNA is then “injected” into the
host cell cytoplasm.
b.) Or that the virus is taken up by
receptor-mediated endocytosis
Recent experimental evidence
supports the latter hypothesis
and suggests that poliovirus
binds to CD155 or PVR and is
taken up by endocytosis
• Immediately after
internalization of the particle,
the viral RNA is released.

7. • Released of the viral RNA
Immediately after internalization of
the particle

8. • The primary determinant of
infection for any virus is its ability to
enter a cell and produce additional
infectious particles.
• The presence of (PVR) Polio Virus
Receptor (CD155) is thought to
define the animals and tissues that
can be infected by poliovirus
• Poliovirus is an enterovirus.
• Infection occurs via the fecal–oral
route, meaning that one ingests the
virus and viral replication occurs in
the alimentary tract.
• Virus is shed in the feces of infected
individuals

9. • Poliovirus uses two key
mechanisms to evade the
immune system.
• First, it is capable of surviving
the highly acidic conditions of
the stomach, allowing the virus
to infect the host and spread
throughout the body via the
lymphatic system.
• Second, because it can replicate
very quickly, the virus overwhelms
the host organs before an immune
response can be mounted.
• Individuals who are exposed to
poliovirus, either through infection
or by immunization with polio
vaccine, develop immunity

10. • In immune individuals, antibodies
against poliovirus are present in the
tonsils and gastrointestinal tract
(specifically IgA antibodies) and are
able to block poliovirus replication;
IgG and IgM antibodies against
poliovirus can prevent the spread
of the virus to motor neurons of
the central nervous system.
• When poliovirus encounters
the nerve cells, the protruding
receptors attach to the virus
particle, and infection begins.

11. • Once inside the cell, the virus
hijacks the cell’s assembly process,
and makes thousands of copies of
itself in hours.
• The virus kills the cell and then
spreads to infect other cells.
• For every 200 or so virus particles
that encounter a susceptible cell,
only one will successfully enter and
replicate.
• In tissue culture, poliovirus enters
cells and replicates in six to eight
hours, yielding 10,000 to 100,000
virus particles per cell.

12. • One way the human immune system
protects itself is by producing
antibodies that engage the protein
covering of the poliovirus, preventing
the virus from interacting with
another cell.
• There are three types of poliovirus: 1,
2, and 3. Type 1 is the most virulent
and common.
• Both the Salk and Sabin
vaccines are “trivalent” that is,
active against all three virus
types.

13. • Type 2 poliovirus has not been
detected anywhere in the world
since 1999.
• A person who gets polio is immune
to future infection from the virus
type that caused the polio.

14. • Most people who get infected with
poliovirus (about 72 out of 100) will
not have any visible symptoms.
• About 1 out of 4 people with
poliovirus infection will have flu-like
symptoms that may include
• They include:
 Sore throat, Fever, Tiredness
 Nausea, Headache, Stomach pain
These symptoms usually last 2 to 5
days then go away on their own

15. • A smaller proportion of people with
poliovirus infection will develop other
more serious symptoms that affect the
brain and spinal cord; Including:
 Paresthesia (feeling of pins and
needles in the legs)
 Meningitis (infection of the covering
of the spinal cord and/or brain)
occurs in about 1 out of 25 people
with poliovirus infection
 Paralysis (can’t move parts of the
body) or weakness in the arms, legs,
or both, occurs in about 1 out of
200 people with poliovirus infection.

16. • Paralysis is the most severe symptom
associated with polio because it can
lead to permanent disability and
death.
• Between 2 and 10 out of 100 people
who have paralysis from poliovirus
infection die because the virus affects
the muscles that help them breathe.
• Even children who seem to fully
recover can develop new muscle
pain, weakness, or paralysis as
adults, 15 to 40 years later. This is
called Post-polio Syndrome.
• Note that “poliomyelitis” (or
“polio” for short) is defined as the
paralytic disease. So only people
with the paralytic infection are
considered to have the disease.

17. • Poliovirus only infects humans. It is
very contagious and spreads through
person-to-person contact.
• An infected person may spread the
virus to others immediately before
and about 1 to 2 weeks after
symptoms appear
• The virus lives in an infected person’s
throat and intestines.
• It enters the body through the
mouth and spreads through contact
with the feces (poop) of an infected
person and, though less common,
through droplets from a sneeze or
cough.
• You can get infected with poliovirus
if you have feces on your hands and
you touch your mouth.

18. • The virus can live in an infected
person’s feces for many weeks. It
can contaminate food and water in
unsanitary conditions.
• People who don’t have symptoms
can still pass the virus to others
and make them sick

19. • Polio vaccine protects children by
preparing their bodies to fight the
polio virus.
• Almost all children (99 children out
of 100) who get all the recommended
doses of vaccine will be protected
from polio.
• There are two types of vaccine
that can prevent polio; namely:
a.) Inactivated Poliovirus
Vaccine (IPV)
b.)

20. • Only IPV has been used in the
United States since 2000.
(Given as an injection in the leg or
arm, depending on the patient’s
age).
• OPV is still used throughout much
of the world.

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