Influenza Viruses Classification - Chapter 9.4

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Questions and Answers

What family do influenza viruses belong to?

  • Retroviridae
  • Paramyxoviridae
  • Arenaviridae
  • Orthomyxoviridae (correct)

How many types of influenza viruses are there?

Three types: A, B, and C

Which of the influenza viruses can infect humans?

All three can infect and cause similar symptoms in humans

If you are immune to one type of influenza, you are also immune to the others.

<p>False (B)</p> Signup and view all the answers

What is the host range of Influenza A?

<p>Humans, pigs, horses, birds, marine mammals</p> Signup and view all the answers

What is the host range of Influenza B?

<p>Humans only</p> Signup and view all the answers

What is the host range of Influenza C?

<p>Humans and pigs</p> Signup and view all the answers

What are the epidemiological characteristics of Influenza A?

<p>Antigenic shift and antigenic drift</p> Signup and view all the answers

What are the epidemiological characteristics of Influenza B?

<p>Antigenic drift only</p> Signup and view all the answers

What are the epidemiological characteristics of Influenza C?

<p>Antigenic drift only</p> Signup and view all the answers

What are the clinical features of Influenza A?

<p>May cause pandemics with significant mortalities in affected young people</p> Signup and view all the answers

What are the clinical features of Influenza B?

<p>Severe disease, generally confined to elderly or high-risk individuals, pandemics not seen</p> Signup and view all the answers

What are the clinical features of Influenza C?

<p>Mild disease, common in children, without seasonality</p> Signup and view all the answers

How many gene segments are in the genome of Influenza A?

<p>8 gene segments</p> Signup and view all the answers

How many gene segments are in the genome of Influenza B?

<p>8 gene segments</p> Signup and view all the answers

How many gene segments are in the genome of Influenza C?

<p>7 gene segments</p> Signup and view all the answers

What is the structure of Influenza A?

<p>10 viral proteins; M2 unique</p> Signup and view all the answers

What is the structure of Influenza B?

<p>11 viral proteins; NB unique</p> Signup and view all the answers

What is the structure of Influenza C?

<p>9 viral proteins; HEF unique</p> Signup and view all the answers

Flashcards

Orthomyxoviridae

A family of viruses that includes influenza viruses.

Influenza virus types

Three main types: A, B, and C.

Human infection with influenza

All three types can infect and cause similar symptoms in humans.

Cross-immunity between Influenza types

False. Immunity to one type does not protect against the others.

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Hemagglutinin (HA)

A viral protein that helps influenza spread.

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Host range of Influenza A

Humans, pigs, horses, birds, marine mammals. A broad range!

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Host range of Influenza B

Humans only. Less adventurous than influenza A.

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Host range of Influenza C

Humans and pigs. A bit more adaptable than B.

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Antigenic shift

Significant changes in HA and NA proteins lead to new strains. Think of it as a major makeover.

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Antigenic drift

Small mutations in HA and NA proteins that occur over time. Think of it as a gradual makeover.

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Epidemiological characteristics of influenza A

Influenza A viruses are known for antigenic shift. The ability to change drastically.

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Epidemiological characteristics of influenza B

Only antigenic drift occurs in Influenza B. A gradual morphing over time.

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Epidemiological characteristics of influenza C

Only antigenic drift occurs in Influenza C. Similar to influenza B, gradual changes.

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Clinical features of Influenza A

Can cause pandemics with significant mortality in young people. Think of it as a major flu outbreak.

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Clinical features of Influenza B

Severe disease, typically affecting the elderly or high-risk individuals. Less widespread than influenza A.

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Clinical features of Influenza C

Mild disease, common in children, without seasonality. Think of it as a weaker flu.

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Genome of influenza A

8 gene segments. Like puzzle pieces that make up the virus.

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Genome of influenza B

8 gene segments. Similar to influenza A in composition.

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Genome of influenza C

7 gene segments. One fewer puzzle piece than influenza A and B.

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Study Notes

Influenza Virus Classification

  • Influenza viruses belong to the Orthomyxoviridae family.
  • There are three main types of influenza viruses: A, B, and C.
  • All three types can infect humans, leading to similar symptoms.
  • Immunity to one type of influenza does not provide protection against the others.

Host Range

  • Influenza A can infect a wide range of hosts: humans, pigs, horses, birds, and marine mammals.
  • Influenza B is limited to humans only.
  • Influenza C can infect both humans and pigs.

Epidemiology

  • Influenza A experiences both antigenic shift and drift, allowing for significant genetic variation.
  • Influenza B undergoes only antigenic drift, resulting in less variation than A.
  • Influenza C also exhibits antigenic drift without significant variation.

Clinical Features

  • Influenza A has the potential to cause pandemics, particularly affecting younger populations with significant morbidity and mortality.
  • Influenza B may lead to severe disease, primarily in the elderly or high-risk groups, but pandemics are not commonly observed.
  • Influenza C typically results in mild disease, particularly in children, and lacks seasonality.

Genome Structure

  • Influenza A and B genomes each consist of 8 gene segments.
  • Influenza C has a genome composed of 7 gene segments.

Viral Structure

  • Influenza A has 10 unique viral proteins, with M2 protein being distinct.
  • Influenza B is characterized by 11 viral proteins, with NB protein as its unique feature.
  • Influenza C contains 9 viral proteins, including the unique HEF protein.

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