Lesson 3.5 - Influenza

Question 1

Spanish Flu Pandemic (1818-19) Overview

Answer 1

• 20 - 40 million deaths worldwide
  
  • US: 675,000
• R₀ = 1.4 - 2.8
• Caused by filterable agent - respiratory transfer
• Koch postulates (ferrets)

Question 2

Infectious Period [Influenza]

Answer 2

1 day before symptoms, and 5-7 days after becoming ill; children may be contagious for weeks

Question 3

What cells does influenza affect?

Answer 3

Ciliated epithelial cells of respiratory tract

Question 4

Symptoms of Influenza

Answer 4

Fever, headache, muscle pain, nasal congestion, sore throat, dry cough

Question 5

At-risk individuals [Influenza]

Answer 5

• Children <5 (esp. <2)
• 65+
• Pregnant
• Long-term facility residents
• Ppl. w/ chronic disorders

Question 6

How much is spent in annual health care costs? [Influenza]

Answer 6

• $11 billion
  
  • DIRECT / Disease management: $3.2 billion
  • INDIRECT / Lost wages, productivity, home/childcare: $8.0 billion

Question 7

Seasonal (or common) flu

Answer 7

• R₀= 0.9 to 2.1
• Some have immunity, vaccine available annually
• Antiviral medications (severe cases)

Question 8

Pandemic flu

Answer 8

• R₀ = 1.47 to 2.27
• Little immunity, easy spread
• Several pandemics during 20th century = millions of deaths

Question 9

R₀ and Death Count of 1918-19 Spanish flu (H1N1)

Answer 9

• R₀= 1.8
• 20-40 million deaths

Question 10

R₀ and Death Count of 1957 Asian Flu (H2N2)

Answer 10

• R₀= 1.57
• 2 million deaths

Question 11

R₀ and Death Count of 1968 Hong Kong Flu (H3N2)

Answer 11

• R₀ = 1.8
• 1 million deaths

Question 12

R₀ and Death Count of 1977-78 Russian Flu (H2N2)

Answer 12

• R₀ = 2.2
• 1 million deaths

Question 13

What type of virus is Influenza?

Answer 13

• (-) sense RNA (Baltimore class V)
  
  • Contain RNA dependent RNA polymerase
    
    • Synthesize (+) strand = mRNA
  • Lacks proofreading = mutations

Question 14

Influenza genome consists of ___ (-) sense ssRNA strands

Answer 14

• 8
  
  • ​1-6 encodes 1 protein
  • 7 & 8 encodes 2 proteins
    
    • 11th gene found on some strand 8

Question 15

___ polymerase subunits make up RNA dependent RNA polymerase [Influenza]

Answer 15

• 3
  
  • ​PB2, PB1, & PA

NP = nucleoprotein

RNP = RNA nucleoprotein

Question 16

Define Hemagglutinin (H) and Neuraminidase (N)

Answer 16

• H: Viral envelope glycoprotein; binds to receptor on eukaryotic/human respiratory cells
• N: hydrolyzes sialic acid; carb covering cell surface; required for penetration & aids budding

*Both are principal antigens recognized by host immune system

Question 17

Influenza A viruses overview

Answer 17

• Infect humans, horses, pigs, ferrets, & birds
• 18* known hemafflutinin (HA) serotypes & 11 known neuraminidase (NA) serotypes

Question 18

Influenza B viruses overview

Answer 18

• Only infects mammals; incites mild influenza in humans
• No distinguishable serotypes

Question 19

Influenza C viruses overview

Answer 19

• Not pathogens
  
  • Only infects animals
• Genetically & morphologically diff. from A & B types

Question 20

How does Influenza enter host cells? (terms: virion, HA, etc.)

Answer 20

• Virion attach to ciliated cells of nose/throat
  
  • Hemagglutinin (HA) surface proteins bind to sialic acid receptors
    
    • Key/lock model
    • Virus enters by endocytosis (vacuole)

Question 21

What happens after virus enters a host cell? [Influenza]

Answer 21

• Viral RNA dependent RNA polymerase makes (+) RNA
  
  • Viral RNA is translated
    
    • RNA dependent RNA polymerase makes (-) RNA from (+) RNA
  • Enveloped viruses don’t always kill host; can continously shed from infected cell

Question 22

Why can Influenza be life-threatening?

Answer 22

• Can lead to secondary bacterial infections that cause pneumonia
  
  • Staphylococcus aureus, Streptococcus pneumonia

Question 23

Define cytokine storm.

Answer 23

• Intense immune reaction that is life-threatening
• Large # of T-cells release pro-inflammatory & anti-inflammatory cytokines
• Lead to pulmonary edema & multisystem organ failure
  
  • Common in <40 y/o

Question 24

Influenza evolves _____.

Answer 24

• RAPIDLY
  
  • ​Due to low fidelity RNA polymerase & no proof-reading
  • Diff. surface glycoproteins

Question 25

Antigenic ____ leads to localized outbreaks.

Answer 25

TOKYOOOO DRIFT

(from low fidelity RNA polymerase)

Question 26

Antigenic ____ leads to pandemics.

Answer 26

SHIFT

(from reassortment)

Question 27

Each year, new strains of influenza emerge from _______.

Answer 27

southern China; domestic pigs serves as host for avian & human influenza viruses

Question 28

Influenza Vaccination Overview

Answer 28

• Flu shot contains 3-4 strains of inactivated virus into deltoid muscle
  
  • Trivalent: 2 influenza A & 1 influenza B
  • Quadrivalent: 2 influenza A & 2 influenza B
• Nasal-spray flu vaccine contains hypovirulent live viruses
  
  • ​Live Attenuated Influenza Vaccine [LAIV]
  • FluMist
• Antibodies develop abt. 2 weeks

Question 29

How effective is the flu vaccine?

Answer 29

• Selection 1 year prior
• Epidemiologists predict what strains likely to cause illness
  
  • Well-matches can reduce chances by 70-90%
• Tremendous return (given the $11 billion healthcarecost)

Question 30

What are antivirals? What are examples?

Answer 30

• Drugs that interfere with viral replicative cycle
  
  • i.e. Influenza Neuraminidase Inhibitors
    
    • Administered for severe cases, but resistant strains exist
  • Amantadine & rimantidine bind to site w/in M2 channel pore

Question 31

2020-21 Influenza Season death toll

Answer 31

292 (1 pediatric flu death)

Question 32

Symptoms of Influenza vs. COVID-19

Answer 32

• Influenza: rare sneezing & SoB, never loss of taste/smell
• COVID-19: rare sneezing, sometimes loss of taste/smell, often SoB

Question 33

Influenza vs. Sars-CoV-2 Comparison Chart

Answer 33

Sars-CoV-2 is deadlier & larger