Lesson 3.5 - Influenza Flashcards
Spanish Flu Pandemic (1818-19) Overview
- 20 - 40 million deaths worldwide
- US: 675,000
- R0 = 1.4 - 2.8
- Caused by filterable agent - respiratory transfer
- Koch postulates (ferrets)
Infectious Period [Influenza]
1 day before symptoms, and 5-7 days after becoming ill; children may be contagious for weeks
What cells does influenza affect?
Ciliated epithelial cells of respiratory tract
Symptoms of Influenza
Fever, headache, muscle pain, nasal congestion, sore throat, dry cough
At-risk individuals [Influenza]
- Children <5 (esp. <2)
- 65+
- Pregnant
- Long-term facility residents
- Ppl. w/ chronic disorders
How much is spent in annual health care costs? [Influenza]
- $11 billion
- DIRECT / Disease management: $3.2 billion
- INDIRECT / Lost wages, productivity, home/childcare: $8.0 billion
Seasonal (or common) flu
- R0= 0.9 to 2.1
- Some have immunity, vaccine available annually
- Antiviral medications (severe cases)
Pandemic flu
- R0 = 1.47 to 2.27
- Little immunity, easy spread
- Several pandemics during 20th century = millions of deaths
R0 and Death Count of 1918-19 Spanish flu (H1N1)
- R0= 1.8
- 20-40 million deaths
R0 and Death Count of 1957 Asian Flu (H2N2)
- R0= 1.57
- 2 million deaths
R0 and Death Count of 1968 Hong Kong Flu (H3N2)
- R0 = 1.8
- 1 million deaths
R0 and Death Count of 1977-78 Russian Flu (H2N2)
- R0 = 2.2
- 1 million deaths
What type of virus is Influenza?
- (-) sense RNA (Baltimore class V)
- Contain RNA dependent RNA polymerase
- Synthesize (+) strand = mRNA
- Lacks proofreading = mutations
- Contain RNA dependent RNA polymerase
Influenza genome consists of ___ (-) sense ssRNA strands
-
8
- 1-6 encodes 1 protein
- 7 & 8 encodes 2 proteins
- 11th gene found on some strand 8
___ polymerase subunits make up RNA dependent RNA polymerase [Influenza]
-
3
- PB2, PB1, & PA
NP = nucleoprotein
RNP = RNA nucleoprotein
Define Hemagglutinin (H) and Neuraminidase (N)
- 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
Influenza A viruses overview
- Infect humans, horses, pigs, ferrets, & birds
- 18* known hemafflutinin (HA) serotypes & 11 known neuraminidase (NA) serotypes
Influenza B viruses overview
- Only infects mammals; incites mild influenza in humans
- No distinguishable serotypes
Influenza C viruses overview
- Not pathogens
- Only infects animals
- Genetically & morphologically diff. from A & B types
How does Influenza enter host cells? (terms: virion, HA, etc.)
- 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)
- Hemagglutinin (HA) surface proteins bind to sialic acid receptors
What happens after virus enters a host cell? [Influenza]
- 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
- Viral RNA is translated
Why can Influenza be life-threatening?
- Can lead to secondary bacterial infections that cause pneumonia
- Staphylococcus aureus, Streptococcus pneumonia
Define cytokine storm.
- 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
Influenza evolves _____.
-
RAPIDLY
- Due to low fidelity RNA polymerase & no proof-reading
- Diff. surface glycoproteins
Antigenic ____ leads to localized outbreaks.
TOKYOOOO DRIFT
(from low fidelity RNA polymerase)
Antigenic ____ leads to pandemics.
SHIFT
(from reassortment)
Each year, new strains of influenza emerge from _______.
southern China; domestic pigs serves as host for avian & human influenza viruses
Influenza Vaccination Overview
- 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
How effective is the flu vaccine?
- 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)
What are antivirals? What are examples?
- 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
- i.e. Influenza Neuraminidase Inhibitors
2020-21 Influenza Season death toll
292 (1 pediatric flu death)
Symptoms of Influenza vs. COVID-19
- Influenza: rare sneezing & SoB, never loss of taste/smell
- COVID-19: rare sneezing, sometimes loss of taste/smell, often SoB
Influenza vs. Sars-CoV-2 Comparison Chart
Sars-CoV-2 is deadlier & larger
