Polio Virus

Polio Virus

Q. 1

All are true about poliovirus, except-

 A

Type I is responsible for most epidemics

 B

Very difficult to eliminate type I

 C

Type I responsible for vaccine paralytic polio myelitis

 D

Type I most commonly associated with paralysis

Q. 1

All are true about poliovirus, except-

 A

Type I is responsible for most epidemics

 B

Very difficult to eliminate type I

 C

Type I responsible for vaccine paralytic polio myelitis

 D

Type I most commonly associated with paralysis

Ans. C

Explanation:

Ans. is ‘c’ i.e., Type I responsible for vaccine induced paralytic poliomyelitis

Polio Virus

.   Belongs to Picornavirus

.    A nonenveloped RNA virus (ss RNA).

.  Has four viral proteins, VP1-VP4. VP 1 Carries the major antigenic site.

.   Three types                   Type I , 2 and 3

Type 1 is most common and causes most epidemics

.     Type 2 usually causes endemic infections

.   Type 3 also causes epidemics.

Pathology

.   Virus multiplies selectively in neurons and destroys them.

Earliest change                             

Chromatolysis (Degeneration of nissel bodies)

– Lesions are mostly in the anterior horns of the spinal cord.


Q. 2

The most predominant type of polio virus during epidemics is 

 A

Type I

 B

Type II

 C

Type III

 D

Combined infection of II & III

Q. 2

The most predominant type of polio virus during epidemics is 

 A

Type I

 B

Type II

 C

Type III

 D

Combined infection of II & III

Ans. A

Explanation:

Ans. is ‘a’ i.e., Type I 

Poliomyelitis

o Poliomyelitis is an acute viral infection caused by poliovirus.

o There are three types of polioviruses –

  • Type 1 —> Most common and causes most epidemics

           Type 2

        Type 3

o No serotype – 2 (type -2) poliovirus has been detected anywhere in the world since 1999, type 1 and type

3 have been detected.

o Peculiar features of different types of virus –

  • Most common cause of epidemic                       —> Type 1

           Most difficult to eradicate                                    —> Type 1

           Vaccine induced paralytic polio                          —> Type 3

           Most commonly associated with paralysis               Type 3

          Most effective antigen                                          —> Type 2


Q. 3

For every clinical case of poliomyelitis subclinical cases are –

 A

500 in, children and 75 in adults

 B

500 in children and 25 in adults

 C

250 in children and 25 in adults

 D

1000 in children and 75 in adults

Q. 3

For every clinical case of poliomyelitis subclinical cases are –

 A

500 in, children and 75 in adults

 B

500 in children and 25 in adults

 C

250 in children and 25 in adults

 D

1000 in children and 75 in adults

Ans. D

Explanation:

Ans. is ‘d’ i.e., 1000 in children and 75 in adults 

o Reservoir of infection —> Man is the only reservoir. Most infections are subclinical and play a dominant role in spread

of infection. It is estimated that for every clinical case, there may be 1000 subclinical cases in children and 75 in adults. o Infectious material —> Feces and oropharyngeal secretion.

o Period of communicability —> 7 to 10 days before and after onset of symptoms.

o Age —> 6 months to 3 years

o Sex –> More in males

o Mode of transmission —> Fecal oral route (major), droplet infection (in developed countries).


Q. 4

Polio virus is shed in stool upto- 

 A

6 weeks

 B

8 weeks

 C

10 weeks

 D

12 weeks

Q. 4

Polio virus is shed in stool upto- 

 A

6 weeks

 B

8 weeks

 C

10 weeks

 D

12 weeks

Ans. D

Explanation:

Ans. is ‘d’ i.e., 12 weeks 

o In the faces, the virus is excreted commonly for 2 to 3 weeks, sometimes as long as 3 to 4 months.


Q. 5

True statement regarding poliomyelitis is:

March 2010

 A

Poliovirus is resistant to pasteurization

 B

For every clinical case, there may be 1000 subclinical cases in adults

 C

Commonly spreads by faeco-oral route

 D

Most outbreaks of polio are due to type-3 poliovirus

Q. 5

True statement regarding poliomyelitis is:

March 2010

 A

Poliovirus is resistant to pasteurization

 B

For every clinical case, there may be 1000 subclinical cases in adults

 C

Commonly spreads by faeco-oral route

 D

Most outbreaks of polio are due to type-3 poliovirus

Ans. C

Explanation:

Ans. C: Commonly spreads by faeco-oral

  1. Poliomyelitis is caused by infection with a member of the genus Enterovirus known as poliovirus (PV). This group of RNA viruses prefers to inhabit the gastrointestinal tract.

PV infects and causes disease in humans alone.

Its structure is very simple, composed of a single (+) sense RNA genome enclosed in a protein shell called a capsid.

Three serotypes of poliovirus have been identified-poliovirus type 1 (PV1), type 2 (PV2), and type 3 (PV3)- each with a slightly different capsid protein.

All three are extremely virulent and produce the same disease symptoms.

PV1 is the most commonly encountered form, and the one most closely associated with paralysis.

The virus may be rapidly inactivated by pasteurization.

Individuals who are exposed to the virus, either through infection or by immunization with polio vaccine, develop immunity.

In immune individuals, IgA antibodies against poliovirus are present in the tonsils and gastrointestinal tract and are able to block virus replication; IgG and IgM antibodies against PV can prevent the spread of the virus to motor neurons of the central nervous system.

Infection or vaccination with one serotype of poliovirus does not provide immunity against the other serotypes, and full immunity requires exposure to each serotype

Poliomyelitis is highly contagious and spreads easily by human-to-human contact.

Incubation period is usually between 7 to 14 days, with a maximum range of 3 to 35 days.

Virus particles are excreted in the feces for several weeks following initial infection.

The disease is transmitted primarily via the fecal-oral route, by ingesting contaminated food or water.

It is occasionally transmitted via the oral-oral route, a mode especially visible in areas with good sanitation and hygiene. Polio is most infectious between 7-10 days before and 7-10 days after the appearance of symptoms, but transmission is possible as long as the virus remains in the saliva or feces

Man is the only known reservoir of infection. Most infections are subclinical. They form the submerged portion of the iceberg.

It is estimated that for every clinical case, there may be 1000 subclinical cases in children and 75 in adults.



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