Influenza virus

Influenza virus

Q. 1

Antigenic variation is NOT seen in which type of influenza virus?

 A

Type A

 B

Type B

 C

Type C

 D

Type A and B

Q. 1

Antigenic variation is NOT seen in which type of influenza virus?

 A

Type A

 B

Type B

 C

Type C

 D

Type A and B

Ans. C

Explanation:

Antigenic variation is not seen in type C influenza virus. Antigenic variability is highest in influenza virus type A and less in type B. 
 
Influenza viruses are remarkable because of the frequent antigenic changes that occur in HA and NA.
The internal RNP antigen and M protein antigen are stable but both the surface antigens, hemagglutinin and neuraminidase undergo independent antigenic variation of two types called antigenic shift or drift in HA or NA resulting in the appearance of a new subtype.
  • Antigenic drift: refers to minor antigenic changes either in hemagglutinin or neuraminidase or both.
  • Antigenic shift: It is an abrupt, drastic discontinuous variation in the antigenic structure resulting in a novel virus strain unrelated antigenically to predecessor strains.
Ref: Textbook of Microbiology By Surinder Kumar page 563.

Q. 2

All the following are true regarding Type A influenza virus, EXCEPT:

 A

There are only 14 subtypes of haemagglutinin

 B

There are only 9 subtypes of neuraminidase antigen

 C

Humans are generally infected by virus of subtype H1, H2 or H3 and N1 or N2.

 D

It shows both antigenic shift and drift

Q. 2

All the following are true regarding Type A influenza virus, EXCEPT:

 A

There are only 14 subtypes of haemagglutinin

 B

There are only 9 subtypes of neuraminidase antigen

 C

Humans are generally infected by virus of subtype H1, H2 or H3 and N1 or N2.

 D

It shows both antigenic shift and drift

Ans. A

Explanation:

There are 16 subtypes of hemagglutinins.

Rest of the statements given are true.

Antigenic changes occurs only to a lesser degree in group B influenza virus.

Influenza C virus appears to be antigenically stable.

Note: Almost all of the pandemic which has ever occurred is due to Type A influenza virus.

Ref: Park, Edition 21, Page – 143,144


Q. 3

The 1997 bird flu pandemic was caused by which of the following strain?

 A

H1N1

 B

H5N1

 C

H2N1

 D

H4N1

Q. 3

The 1997 bird flu pandemic was caused by which of the following strain?

 A

H1N1

 B

H5N1

 C

H2N1

 D

H4N1

Ans. B

Explanation:

Human infections with avian influenza H5N1 was first reported in Hong Kong in 1997.

Ref: Epidemiology of communicable diseases

Park’s textbook of Preventive and Social Medicine, 21stedition, page-330.


Q. 4

Influenza virus culture is done on ‑

 A

Chorioallantoic membrane 

 B

Allantoic cavity

 C

Yolk sac

 D

All

Q. 4

Influenza virus culture is done on ‑

 A

Chorioallantoic membrane 

 B

Allantoic cavity

 C

Yolk sac

 D

All

Ans. B

Explanation:

Ans. is b i.e., Allantoic cavity

In embryonated egg cultivation for influenza virus site of inoculation are :- Allontoic cavity or amniotic cavity

Inoculation sites in embryonated eggs

  • Chorioallantoic membrane          -4 HSV, Poxvirus, Rous-sarcoma virus
  • Amniotic cavity                          -4 Influenza virus, mumps virus
  • Allantoic cavity                           –  Influenza virus, mumps virus, avian adenovirus, newcastle disease virus
  • Yolk sac                                   –> HSV, chlamydia, rickettisia    




Q. 5

At present following types of influenza viruses are circulating in the world, except ‑

 A

HIM

 B

H3N2

 C

H5N,

 D

B virus

Q. 5

At present following types of influenza viruses are circulating in the world, except ‑

 A

HIM

 B

H3N2

 C

H5N,

 D

B virus

Ans. C

Explanation:

Ans. is ‘c’ i.e., H5N,

  • At present three types of influenza viruses are circulating in the world: A(H/N1), A (H3N2) and B viruses.
  • WHO global surveillance activities have identified human infection with a new influenza virus called A ) in Hong Kong in mid1997. However, the possibility that the outbreak heralded a global influenza pandemic did not materialize.

Q. 6

True statement about influenza A is –

 A

It has a double stranded segmented RNA

 B

Pandemic are caused by antigenic drift

 C

Nucleocapsid antibody is not specific

 D

Hemagglutinin and Neuraminidase is strain specific

Q. 6

True statement about influenza A is –

 A

It has a double stranded segmented RNA

 B

Pandemic are caused by antigenic drift

 C

Nucleocapsid antibody is not specific

 D

Hemagglutinin and Neuraminidase is strain specific

Ans. D

Explanation:

Ans. is ‘d’ i.e., Hemagglutinin and Neuraminidase is strain specific


Q. 7

True about influenza –

 A

Epidemic is due to antigenic drift

 B

Has double standed RNA

 C

Nucleocapsid is protective

 D

All

Q. 7

True about influenza –

 A

Epidemic is due to antigenic drift

 B

Has double standed RNA

 C

Nucleocapsid is protective

 D

All

Ans. A

Explanation:

Ans. is ‘a’ i.e., Epidemic is due to antigenic drift


Q. 8

Causes of antigenic drift in influenza viral infections‑

 A

Small mutation in neuraminidase and hemagglutinin

 B

Large mutations in hemagglutinin only

 C

Step mutations in viral genome

 D

None of the above

Q. 8

Causes of antigenic drift in influenza viral infections‑

 A

Small mutation in neuraminidase and hemagglutinin

 B

Large mutations in hemagglutinin only

 C

Step mutations in viral genome

 D

None of the above

Ans. A

Explanation:

Ans. is ‘a’ i.e., Small mutation in neuraminidase and hemagglutinin


Q. 9

Incubation period of influenza

 A

18 – 72 hrs

 B

1 – 6 hrs

 C

5 – 10 days

 D

< 1 hrs

Q. 9

Incubation period of influenza

 A

18 – 72 hrs

 B

1 – 6 hrs

 C

5 – 10 days

 D

< 1 hrs

Ans. A

Explanation:

Ans. is ‘a’ i.e., 18 – 72 hrs


Q. 10

True about epidemology of influenza – 

 A

Asymptomatic seen rarely

 B

Incubation period 10-12 hrs

 C

Pandemic rare

 D

All ages sex are equally affected

Q. 10

True about epidemology of influenza – 

 A

Asymptomatic seen rarely

 B

Incubation period 10-12 hrs

 C

Pandemic rare

 D

All ages sex are equally affected

Ans. D

Explanation:

Ans. is `D’ i.e., All ages sex are equally affected 

  • Influenza affects all ages and both sexes.

About other options

o Most infections are subclinical.

o Incubation period is 18-72 hours.

o Influenza causes pandemic every 10-15 years.

o Major reservoir of influenza virus exists in animal and birds.


Q. 11

Which of the following lead to an outbreak of Influenza in China in 2013 –

 A

H1N1

 B

H3N2

 C

H2N2

 D

H7N9

Q. 11

Which of the following lead to an outbreak of Influenza in China in 2013 –

 A

H1N1

 B

H3N2

 C

H2N2

 D

H7N9

Ans. D

Explanation:

Ans. is ‘d’ i.e., H7N

  • In china, there was an outbreak of influenza caused by Avian influenza H7N9, in 2013.
  • It started in china and spread to Hong Kong.
  • Most common age group affected was older male (> 50 years).

Q. 12

Influenza pandemic shows which type of trend:

September 2009, March 2013 (d, f)

 A

Secular

 B

Cyclical

 C

Seasonal

 D

None of the above

Q. 12

Influenza pandemic shows which type of trend:

September 2009, March 2013 (d, f)

 A

Secular

 B

Cyclical

 C

Seasonal

 D

None of the above

Ans. B

Explanation:

Ans. B: Cyclical

Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae (the influenza viruses), that affects birds and mammals.

These viruses are only distantly related to the human parainfluenza viruses, which are RNA viruses belonging to the paramyxovirus family that are a common cause of respiratory infections in children such as croup.

Sore throat, fever and coughs are the most frequent symptoms.

In more serious cases, influenza causes pneumonia, which can be fatal, particularly for the young and the elderly. Typically, influenza is transmitted through the air by coughs or sneezes, creating aerosols containing the virus.

Influenza can also be transmitted by direct contact with bird droppings or nasal secretions, or through contact with contaminated surfaces.

Influenza viruses can be inactivated by sunlight, disinfectants and detergents. As the virus can be inactivated by soap, frequent hand washing reduces the risk of infection.

Influenza pandemics show cyclical trend and are known to occur at intervals of 740 years, due to antigenic variations.


Q. 13

Single stranded RNA with segmented genes is found in ‑

 A

Influenza

 B

Rotavirus

 C

Reovirus

 D

Measles virus

Q. 13

Single stranded RNA with segmented genes is found in ‑

 A

Influenza

 B

Rotavirus

 C

Reovirus

 D

Measles virus

Ans. A

Explanation:

Ans. is ‘a’ i.e., Influenza

Some viruses have segmented nucleic acid (genome).

These are (Mnemonic BORA) :‑

1) Bunyaviridae : 3 segments of single stranded RNA.

2) Orthomyxoviridae (influenza) : 8 segments of single stranded RNA.

3) Reoviridae (rotavirus, reovirus) : 10-12 segments of double stranded RNA.

4) Arenaviridae : 2 segments of single stranded RNA.


Q. 14

Virus which has more than one serotypes ‑

 A

Measles

 B

Mumps

 C

Rubella

 D

Influenza

Q. 14

Virus which has more than one serotypes ‑

 A

Measles

 B

Mumps

 C

Rubella

 D

Influenza

Ans. C

Explanation:

Ans. is ‘d’ i.e., Influenza

Influenza virus is an enveloped RNA virus containing 8 pieces (8 segments) of single stranded RNA.

There are three viral subtypes : (i) Type A (causes all pandemics and most epidemics); (ii) Type B; and (iii) Type C (not circulating currently).


Q. 15

Influenza virus belongs to family ‑

 A

Picornaviridae

 B

Calciviridae

 C

Orthomyxoviridae

 D

Paramyxoviridae

Q. 15

Influenza virus belongs to family ‑

 A

Picornaviridae

 B

Calciviridae

 C

Orthomyxoviridae

 D

Paramyxoviridae

Ans. C

Explanation:

Ans. is ‘c’ i.e., Orthomyxoviridae


Q. 16

Influenza pandemic is ‑

 A

Seasnal trend

 B

Cyclic trend

 C

Secular tred

 D

None of the above

Q. 16

Influenza pandemic is ‑

 A

Seasnal trend

 B

Cyclic trend

 C

Secular tred

 D

None of the above

Ans. B

Explanation:

Ans. is ‘b i.e., Cyclic trend


Q. 17

Prevalence of Influenza in India ‑

 A

10 per 10000 population

 B

10 per 100000 population

 C

10 per 1000 population

 D

Data regarding prevalence of influenza is not adequate

Q. 17

Prevalence of Influenza in India ‑

 A

10 per 10000 population

 B

10 per 100000 population

 C

10 per 1000 population

 D

Data regarding prevalence of influenza is not adequate

Ans. D

Explanation:

Ans. is ‘d’ i.e., Data regarding prevalence of influenza is not adequate


Q. 18

True about influenza ‑

 A

Incubation period 2-3 weeks

 B

Most infections are subclinical

 C

Type-A virus causes Reye’s syndrome

 D

Pandemic is caused by Type-B virus

Q. 18

True about influenza ‑

 A

Incubation period 2-3 weeks

 B

Most infections are subclinical

 C

Type-A virus causes Reye’s syndrome

 D

Pandemic is caused by Type-B virus

Ans. B

Explanation:

Ans. is ‘b’ i.e., Most infections are subclinical

Influenza

  • Influenza virus a RNA virus, belongs to orthomyxovirus.
  • There are three viral subtypes : i) Type A (causes all pandemics and most epidemics); type B; and type C (not circulating currently).
  • Currently the influenza viruses circulating in the world are : 111 N, of type A (causes swine flu); H2 N2 of type A; H3 N2 of type A ; H5 NI of type A (causes birdflu or avian influenza); H7 N9 of type A (caused epidemic of avian influenza in China in 2013); and type B.
  • Influenza shows cyclic trend with epidemic occuring every 2-3 years in case of influenza – A and every 4-7 years in case of influenza-B. Pandemics are caused by only influenza – A every 10-15 years.
  • Influenza affects all ages and both sexes.
  • Source of infection of influenza is a clinical case or subclinical case.
  • Major reservoir of influenza virus exists in animal and birds.
  • Incubation period is 18-72 hours. Most of the infections are subclinical. Clinical cases present with cough, fever, myalgia and headache.

Q. 19

Which of the following statemnets are true regarding the virus shown in the picture below?

a) Antigenic shift causes pandemics 
(b) Antigenic drift is seen in Influenza A and B
(c) Type A only cause epidemic 

 A

(a) (b) True & (c) False.

 B

(a) (b) & (c) False.

 C
(a) (b) False & (c) True.
 D

(a) (b) & (c) True.

Q. 19

Which of the following statemnets are true regarding the virus shown in the picture below?

a) Antigenic shift causes pandemics 
(b) Antigenic drift is seen in Influenza A and B
(c) Type A only cause epidemic 

 A

(a) (b) True & (c) False.

 B

(a) (b) & (c) False.

 C
(a) (b) False & (c) True.
 D

(a) (b) & (c) True.

Ans. D

Explanation:

Ans:D.)(a) (b) & (c) True.

The virus shown in the picture above represents influenza virus.

INFLUENZA VIRUS

IClassified into A, B and C – based on RNP and M protein antigens

    • Antigenic variation is highest in type A, less in type B and not seen in type C
      • Type A – pandemics(an epidemic of world-wide proportions).
      • Type B – sporadic and epidemics
      • Type C – endemic throughout the world

Antigenic Shift and Drift

  • Antigenic drift occurs in both influenza A and influenza B viruses.
    Antigenic shift, however, occurs only in influenzavirus A because it infects more than just humans and Causes major epidemics and pandemic


Q. 20

Aerosol spread leading to epidemics is seen in infection with:

 A

Legionella

 B

Hemophilus

 C

 Influenza

 D

 Mycoplasma

Q. 20

Aerosol spread leading to epidemics is seen in infection with:

 A

Legionella

 B

Hemophilus

 C

 Influenza

 D

 Mycoplasma

Ans. C

Explanation:

Ans. c. Influenza


Q. 21

Influenza virus has ‑

 A

5 segments of SS RNA

 B

8 Segments of ds DNA

 C

8 segments of ssDNA

 D

8 segments of ssRNA

Q. 21

Influenza virus has ‑

 A

5 segments of SS RNA

 B

8 Segments of ds DNA

 C

8 segments of ssDNA

 D

8 segments of ssRNA

Ans. D

Explanation:

Ans. is ‘d’ i.e., 8 segments of ssRNA 

Influenza virus

  • Belong to orthomyxoviridae  → Envelope, RNA virus
  • Contain single stranded RNA which is segmented  → 8 pieces 


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