Influenza Virus and Vaccine Flashcards
What does influenza A infect?
- humans, swine, and avians (equines, marine mammals, bats, dos)
- capable of antigenic drift and shift
- cause of most epidemics and all pandemics
What does influenza B infect?
- humans and seals
- capable of genetic drift
- rare epidemic and no pandemic
What is the cause of influenza being able to reinfect people and the reason the flu vaccine is changed?
- antigenic drift: small changes in virus (mutation)
- specific mutation: in hemagglutinin envelope protein which allows the virus to escape neutralizing antibodies
What type of virus is influenza?
- orthomyxovirus
- negative sense
- segmented RNA (8 segments)
- helical
- enveloped
How is influenza spread?
- person to person via respiratory droplets and fomites
How is influenza killed?
detergents, heat, acid, or drying due to enveloped virus
Why should you NEVER give aspirin for influenza or chickenpox?
- lead to Reye syndrome due to salicylate causing mitochondrial dysfunction
Do people die with influenza?
Yes… most deaths are people older than 65
- people who are hospitalized are usually due to underlying health conditions and children
What is the difference in children and adults in the pathogenesis of influenza?
- adults shed virus one day before symptoms to 5-7 days after
- children shed up to 10 days after symptoms
How does pneumonia occur usually from influenza?
- usually secondary bacterial pneumonia
- if primary viral pneumonia from influenza, high fatality rate
How can even the healthy get a secondary bacterial pneumonia infection?
- killing airway epithelial cells make it easier for bacteria to bind in airway
- influenza can kill alveolar macrophages that help prevent bacterial infection
- airway edema and dead cells create nutrient rich environment for bacterial growth
- viral neuraminidase inactivates some innate antimicrobials that might help kill bacteria and expose bacterial attachment sites
Why does the flu change from year to year?
- antigenic drift in hemagglutinin
In the pathogenesis of influenza, what does the viral hemagglutinin bind to?
silica acid: a2-6 linkage
- present in the upper respiratory tract at high levels and only in lower respiratory tract at low levels
What are the types of flu vaccines?
- inactivated influenza vaccine: detergent disrupted inactivated virus with HA and NA put in the vaccine
- live attenuated influenza vaccine: cold adapted influenza virus containing HA and NA in the inactivated vaccine
- subunit vaccine: entirely recombinant HA protein grown in cell culture
all are quadrivalent meaning they contain 2 strains of influenza A and 2 strains of influenza B
How is the vaccine for influenza picked up?
- vaccine is picked up before the flu season where strains of influenza are prevalent in other parts of the world
How long does it take to be protected after vaccination?
- 2 weeks
What are the neuraminidase inhibitors and what are the MOA?
- Zanamivir and Oseltamivir: Tamiflu
- MOA: prevent budding and release of virus so must be used within 2-3 days of infection to have maximal effect
- has side effects of nausea and vomitting
How does Baloxzvir/Xofluza work?
- cap-dependent endonuclease inhibitor
- MOA: blocks ability of virus to snatch caps so can’t transcribe viral mRNA
- also must be used within 48 hours
How many people were infected in the 1918 flu epidemic?
- 1/3 to 1/2 of world’s population
- fatality rate of over 2.5%
- W shaped mortality curve: more deaths in 18-40 age range than normal
What’s the difference between avian strain and the human strain?
Avian strain:
- recognizes a2,3 sialic acid linkage
- present in more of lower respiratory tract
- so more severe infection, but less spread
Human strain:
- recognizes a2,6 sialic acid linkage
- present in more of upper respiratory tract
- so not as severe because not much in lower tract, but easily spread
What made the 1918 strain so fatal… what’s the difference between that and the seasonal one now?
- had the PB1-F2 virulence factor
- it could infect both upper and lower respiratory tracts, so severe and efficient person-to-person spread
- replicated more efficiently, cause apoptosis CD8 and alveolar macrophages which increases inflammatory response and increases cellular infiltrates of lung airways (cytokine storm)
- almost all recorded deaths showed bacterial confection (93%)
- little prior immunity in population
How is bird flu spread?
- birds excrete influenza in droppings
- most infections occur from contact with birds (domestic poultry)
- not usually person-to-person spread
What is HPA1/LPA1?
- high pathogenic or low pathogenic avian influenza
- based on ability of virus to kill chickens; not humans
What are the 2 main avian influenzas in bird flue that has crossed over to infect humans in substantial numbers?
- H5N1: 31-53% fatality; HPAI influenza; can cause devastation in poultry industry
- H7N9: 45% fatality; LPAI and HPAI influenzas
What has China been doing in regards to vaccines for bird flu?
vaccinating poultry with an H5/H7 vaccine
