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Patho > Influenza > Flashcards

Influenza Flashcards

1
Q

What are the 3 main types of the influenza virus?

A
  1. Type A
  2. Type B
  3. Type C
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2
Q

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

A

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

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3
Q

What are the primary reserviors of Type A influenza?

A

Waterfowl - virus found in intestines and is released in feces

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4
Q

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

A

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

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5
Q

What two variations dictate the name of virus strains in influenza A?

A

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

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6
Q

What is hemagglutinin?

A

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

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7
Q

What is neuraminidase?

A

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

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8
Q

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

A

H1, H2, H3

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9
Q

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

A

H1N1 from 1918
H3N2 from 1968
H2 has stopped circulating

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10
Q

What are 3 characteristics of influenza type B

A
  1. Are normally exclusive to humans
  2. Are not classified by H and N proteins
  3. Can only cause epidemics, not pandemics
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11
Q

What are the two antigenic lineages of type B influenza?

A

Yamagata & Victoria
Have been circulating since 1980

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12
Q

Why can’t Type B Influenza cause pandemics?

A

Type B viruses undergo antigenic drift less rapidly than Type A viruses
Because they mutate 2-3x slower, there are less subtypes

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13
Q

What hosts are Type C influenza found in?

A

Humans and pigs

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14
Q

What are 2 characteristics of Type C influenza?

A
  1. Less common than the other two types of influenza
  2. Triggers a mild respiratory illness, sometimes no symptoms at all
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15
Q

What causes changes in the H and N proteins?

A

Influenza A genome has 8 single-strands of RNA - if/when they become shuffled or replaced, it results in changes in the H and N protein configuration = creates a new subtype

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16
Q

How does the immune system target influenza viruses?

A

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

17
Q

What are the two purposes of the flu vaccine?

A
  1. To prevent carriers from spreading the virus
  2. To develop herd immunity
18
Q

What is herd immunity?

A

The resistance of a population to a spread of an infectious disease due to the high proportion of the population that has immunity

19
Q

Who does herd immunity protect? (2)

A
  1. Those who cannot or wall not get vaccinated
  2. Those who have an incomplete response to the vaccine
20
Q

What is the purpose of mass vaccinations?

A
  1. To obtain herd immunity
  2. Protect others
21
Q

What are 3 reasons for vaccine hesitancy?

A
  1. Misinformation and mistrust
  2. Worry for personal safety
  3. Mismatch or poor uptake
22
Q

Why are some flu seasons worse than others?

A
  1. Poor vaccine match to virus
  2. Low immunizations rates in the public
  3. Poor uptake of vaccine
23
Q

What is antigenic shift?

A

An abrupt change in H & N protein combination that results in a new/novel combination

24
Q

Explain antigenic shift 1.

A
  • 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
25
Q

Explain antigenic shift 2

A

**no genetic change to virus occurs
bird strain jumps directly to humans and has potential for human-to-human spread

26
Q

Explain antigenic shift 3

A

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

27
Q

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

A

Antigenic shift 1 because genetic changes occur and result in a new strain of a virus that humans have little to no protection against

28
Q

What is antigenic drift?

A

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

29
Q

What type of antigenic changes is responsible for the need for new flu vaccines?

A

Antigenic drift - flu vaccines must be updated yearly as the virus continues to modify and become unrecognizable to the immune system’s previously created antibodies

Patho (9 decks)

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