Test Two: Module 6 Influenza

Question 1

What is influenza and what is its infectious period?

Answer 1

1) Acute respiratory infection due to influenza virus
2) 1-2 days before to 4-5 days after onset
you may be able to pass on the flu to someone else before you know you are sick, as well as while you are sick
* Incubation period of 1-5 days

Question 2

How is influenza spread?

Answer 2

Spreads from person to person through coughing and sneezing
Transmitted by:
inhaling respiratory aerosols containing the virus, produced when infected person talks, coughs, or sneezes
touching an infected person or an item (fomite) contaminated with the virus and then touching your eyes, nose, or mouth (few minutes to 48 hours… depending..

Question 3

What types of animals are infected by the three forms of Influenza A, B, and C?

Answer 3

1) A- infect birds, animals/humans
* Cause seasonal influenza epidemics/pandemics
2) B, C only affect humans (no pandemics)

Question 4

What are the two surface glycoproteins used to distinguish different types of Influenza type A? How many of each kind exist?

Answer 4

1) Hemagglutinin, 16 types of H, H1 through H16

2) Neuraminidase, 9 types of N, N1 through N9

Question 5

Explain the identification:

A/Hong Kong/1/68(H3N2)

Answer 5

1) Type A
2) First isolated in Hong Kong
3) Isolate 1 (out of a number of possible isolate)
4) 1968
5) H3 and N2 surface combination

Question 6

Explain how a virus replicates:

Answer 6

1) Attaches to a receiving cell with appropriate glycoprotein on surface to match the glycoprotein on flu virus
2) Penetrates the cell membrane
3) DNA sequence in genes is copied into a messenger RNA (mRNA). Ribosomes then read the information in this RNA and use it to create proteins. This process is known as translation; i.e., the ribosome “translates” the genetic information from RNA into proteins
4) Golgi apparatus … is another packaging organelle
5) Breaks apart sends RNA of virus nucleus into cell nucleus
6) Transplicing of Viral RNA to DNA of cell
7) New Flu virions (particles) are produced

Question 7

What role does Hemagglutinin play in viral replication?

Answer 7

binding to polysaccharide chains on the cell surface and then injecting the viral genome into the cell

Question 8

What role does Neuraminidase play in viral replication?

Answer 8

, plays its major role after the virus leaves an infected cell. It ensures that the virus doesn’t get stuck on the cell surface by clipping off the ends of these polysaccharide chains.

Question 9

What is Influenza Antigenic Drift?

Answer 9

gradual change in Influenza A and B virus antigens due to point mutations in H and N which create new markers that may make the virus more virulent

Question 10

What is Antigenic Shift?

Answer 10

Dramatic changes to viral genome 
(H and N glycoproteins)
Novel sub-type
Influenza A only
Source: 
Direct animal-to-human transmission
Mixing of human and animal viral genes
Within same individual *(Reassortment)

Question 11

What is responsible for the minor changes in influenza from season to season?

Answer 11

antigenic drift

Question 12

What is responsible for dramatic shifts in the influenza genome?

Answer 12

antigenic shift

Question 13

What is the source of the influenza type A virus?

Answer 13

Human influenza A viruses start as avian (bird) influenza viruses

Question 14

What causes a pandemic?

Answer 14

Pandemics occur when a new (novel) avian influenza strain acquires the ability infect people and to spread easily person to person

Question 15

What are two ways a novel influenza strain can appear?

Answer 15

1) Reassortment (shift) (an exchange of seasonal and avian influenza genes in a person or pig infected with both strains)
2) Mutation (an avian strain becomes more transmissible through adaptive mutation of the virus during human avian influenza infection)

Question 16

Contrast seasonal vs. pandemic influenza:

Answer 16

• Seasonal usually only causes severe disease in very young, very old or people with weak immune systems (already sick)
• Pandemic influenza is much more widespread and can infect and kill young, healthy people.

Question 17

What age group experienced the highest mortality rate during the 1918-1919 pandemic?

Answer 17

People aged 20-40

Question 18

Explain the etymology of influenza:

Answer 18

1) Comes from greek word “influentia” meaning flow of liquid or influence.
2) Used to express belief in the impact of the stars on appearance of epidemics

Question 19

Why is the Spanish Flu of 1918-1919 known as the “Mother of all pandemics”?

Answer 19

All influenza A pandemics since tht time and indeed almost all cases of influenza A world wide have been caused by descendants of the 1918 virus, including “drifted” H1N1 viruses and reassorted H2N2 and H3N2 viruses

Question 20

How many waves did the Spanish flu come in and what were the mortality rates relative to those waves?

Answer 20

1) June/July in major cities of US and Europe… relatively minor
2) Second Wave – October and November much greater mortality
3) Third wave Februrary/March 1919 high mortality

Question 21

How many U.S. deaths were recorded from the Spanish influenza of 1918-1919?

Answer 21

675,000

Question 22

What is thought to be the strain that caused the Spanish influenza and where might it have originated?

Answer 22

H1N1; Pig farmers in Haskell County, Kansas (swine flu) then moved to Fort Funston (Riley) in Kansas

Question 23

What particular age group/ demographic were particularly susceptible to the H1N1 virus?

Answer 23

Young people aged 20-40, especially those in the army. It seemed to move from camp to camp and then overseas to more soldiers.

Question 24

How many estimated deaths world-wide occurred because of the Spanish flu?

Answer 24

40-50 million

Question 25

What is the role of vaccines in prevention against new pandemics?

Answer 25

1) Vaccines take 4-6 months to produce
2) Old vaccines would not protect against a new virus and the virus would need to be identified before a new vaccine can be made.