Influenza

Question 1

3 Types of Influenza Viruses

Answer 1

A, B and C

Question 2

What is the only type of influenza that can cause pandemics?

Answer 2

Type A Influenza – pandemic occurs when virus crosses from birds to humans and has the ability to pass between humans & people have little to no immunity

Question 3

What are the primary reserviors of Type A influenza?

Answer 3

Waterfowl - virus found in intestines and is released in feces

Question 4

Where has ideal conditions for transmission and jumping species of Type A influenza?

Answer 4

Asia - poultry, ducks, pigs, and humans all live in crowded conditions
- also wet-markets

Question 5

What variations dictate the names for Type A influenzas?

Answer 5

Strains named after their H and N variations
H - Hemaggluttinin
N - Neuraminidase

Question 6

What is hemagglutinin?

Answer 6

A type of protein spike on influenza viruses that allows the virus to attach to the host cell and enter via membrane fusion

Question 7

What is neuraminidase?

Answer 7

A type of protein spike on influenza viruses that cuts the host cell membrane, allowing the new virion to be released

Question 8

What are the only H subtypes of influenza A that have shown the ability to transmit freely among humans?

Answer 8

H1, H2, H3

Question 9

How many subtypes of influenza A are still circulating in humans and what are they?

Answer 9

H1N1 from 1918
H3N2 from 1968
H2 has stopped circulating

Question 10

What are the 3 characteristics ofType B influenza

Answer 10

1. Exclusive to human
2. Cause epidemics but not pandemics (slow to replicate)
3. Is not classified by H and N

Question 11

What are the 2 type B influenza lineages?

Answer 11

Yamagata and Victoria (circulating since 1980’s)

Question 12

Why can’t Type B Influenza cause pandemics?

Answer 12

Type B viruses undergo antigenic drift less rapidly than Type A viruses

Because they mutate 2-3x slower, there are less subtypes

Question 13

What hosts are Type C influenza found in?

Answer 13

Humans and Pigs

Question 14

What are 2 characteristics of Type C influenza?

Answer 14

1. Less common than the other two types of influenza
2. Triggers a mild respiratory illness, sometimes no symptoms at all

Question 15

What causes changes in the H and N proteins?

Answer 15

The shuffling or replacing of the 8 strands of influenza A RNA

Question 16

How does the immune system target influenza viruses?

Answer 16

By the spike proteins – if the proteins change, it can affect the virus’s antigenicity

Question 17

What is antigenic SHIFT?

Answer 17

Abrupt change where the H and/or N are replaced with new or novel H or H/N combinations that are completely new to the immune system

Question 18

Herd immunity

Answer 18

When a high % of the population is immune to a disease resulting in less spread

Question 19

What is the purpose of mass vaccination?

Answer 19

To obtain herd immunity to protect those who did not receive a vaccine or those individuals who may have had an incomplete response to a vaccine

Question 20

Antigenic shift 1

Answer 20

• Bird passes bird strain to intermediate carrier
• Person passes human strain to the same intermediate carrier
• Viruses infect the same cell = strain genes mix = creates new strain
• New strain passed back to human from intermediate host

Question 21

Antigenic Shift 2

Answer 21

*** No genetic
a bird strain of influenza A can jump directly from a
duck or other aquatic bird to humans.

Question 22

Antigenic Shift 3

Answer 22

**no genetic change to virus occurs
bird strain jumps directly to intermediate host, then to humans; potential for human-to-human spread

Question 23

What type of antigenic shift can result in a pandemic and why?

Answer 23

ALL due to human to human spread and if there is change in genetic material

Question 24

What is antigenic drift

Answer 24

The continuous process of minor modifications to the virus in circulation as a result of transcription error, resulting in different variants
* when antibodies no longer recognize the variant, reinfection can occur

Question 25

Why are some flu seasons worse than others?

Answer 25

Vaccine mismatch
Poor uptake of the vaccine
Decreased rate of immunization