Microbio Week 11 - Influenza (Exam 3) Flashcards
How many types of influenza are there?
3
What does influenza A infect?
Humans
Swine
Avians
What is influenza A capable of?
Antigenic drift AND shift
What does human influenza combine?
Hemagglutinin (HA) 1, 2, or 3 with neuraminidase (NA) 1 or 2
Which influenza is the cause of most epidemics and all pandemics?
Influenza A
What does influenza B infect?
Humans
What is influenza B capable of?
Antigenic drift
What can result in reinfection and changing the vaccine in influenza B? (ON EXAM)
Antigenic drift
What influenza has rare epidemics but no pandemics?
Influenza B
Results in small changes in the virus
Antigenic drift
Large changes; the swapping of viral RNA segments between human and avian, human and swine, or all three viruses
Antigenic shift
Where are the most critical mutations as a result of antigenic drift?
Hemagglutinin envelope protein
What do mutations in hemagglutinin have the potential to allow?
Allows the virus to escape neutralizing ABs
What will enable the virus to reinfect people and is a reason the change the flu vaccine?
Antigenic drift in hemagglutinin
_______ are the perfect mixing place for antigenic shift, as both human and avian influenza can infect them.
This mixing can sometimes lead to a vastly new virus that can cause a ___________
Pigs; pandemic
How is influenza spread?
Respiratory droplets
Fomites
What type of virus is influenza - naked or enveloped?
Enveloped
T/F: Since influenza is enveloped, it can be killed with detergents, heat, acid, and drying
True
What is the typical number of deaths in the flu season? What population has the most deaths?
<1/1000
Most deaths are people > 65 years old
T/F: Most hospitalizations occur in people with underlying health conditions, but previously healthy adults and children are hospitalized, and some die yearly
True
A pandemic strain of influenza will become the new sessional influenza until supplanted by what?
A new pandemic strain
Are influenza infections local or generalized? How long is the incubation time for influenza infections?
Local infection; short incubation time
How long do symptoms of influenza last?
2-3 days, can be up to 5
When do adults shed the influenza virus?
1 day before symptoms to 5-7 days after
Children can shed the influenza virus up to ____ days after symptoms
10
1/3 of all influenza deaths are due to what?
Secondary bacterial pneumonia
T/F: Pneumonia caused by influenza
(primary viral pneumonia) is rarer than bacterial pneumonia, but is generally worse and has a high fatality rate
True
What does hemagglutinin bind to?
Sialic acid
Which sialic acid linkage does the human influenza virus bind to?
a2-6 linkage
Where is the a2-6 linkage found in the body?
Upper respiratory tract (HIGH levels)
Lower respiratory tract (LOW levels)
Bacterial pneumonia is most prevalent in people with underlying _______ problems, but even the healthy can
get secondary bacterial infections
lung
How does secondary bacterial pneumonia occur in influenza infections? (4)
- Killing airway epithelial cells makes it easier for bacteria to bind in the airway
- Influenza kills alveolar macrophages that help prevent bacterial infection
- Airway edema and dead cells create a nutrient-rich environment for bacterial growth
- Viral neuraminidase inactivates some innate antimicrobials that might help kill bacteria and expose bacterial attachment sites
Which vaccine?
A detergent disrupted inactivated virus. Just the HA and NA are
isolated and put in the vaccine
Inactivated influenza vaccine (IIV)
Which vaccine?
Contains a cold-adapted influenza virus containing the HA and NA
in the inactivated vaccine
Live attenuated influenza vaccine (LAIV)
Which vaccine?
Contains an entirely recombinant HA protein grown in cell culture
Subunit vaccine (RIV)
All influenza vaccines will be _________
trivalent
What does the trivalent vaccine contain?
2 strains of influenza A
1 strain of influenza B
Protection from infection is achieved how long after vaccination?
2 weeks
Zanamivir and Oseltamivir (Tamiflu) are _____________ inhibitors
neuraminidase
What do Zanamivir and Oseltamivir (Tamiflu) prevent?
Prevent the budding and release of the virus
Zanamivir, Oseltamivir (Tamiflu), and Baloxzvir (Xofluza) must be used within ____ to _____ days of infection to have max. effect
2 to 3
Baloxzvir (Xofluza) is a cap-dependent ______________ inhibitor
endonuclease
What does Baloxzvir (Xofluza) block?
Blocks the virus from “snatching caps” and transcribing viral mRNA
T/F: Baloxzvir (Xofluza) is as effective as neuraminidase inhibitors
True
How many people were infected during the 1918 flu epidemic?
1/3 to 1/2 world population
What was the fatality rate during the 1918 flu epidemic?
> 2.5%
The 1918 flu epidemic had a W-shaped mortality curve, meaning what?
There were more deaths in the 18-40 year age than normal for influenza
What 3 things make a highly virulent strain of influenza?
- Receptor usage
- Viral virulence factor present in avian flu and 1918 flu, but not in human influenzas
- Little immunity to the new virus
What sialic acid linkage do avian strains recognize?
a2-3
Where is the a2-3 sialic acid linkage (avian strain) found in the body?
Upper respiratory tract (LOW levels)
Lower respiratory tract (HIGH levels)
What does the avian strain cause?
More severe LRT infection
Less spread from person to person
What does the human strain cause (a2-6 linkage)?
Less chance of LRT infection
More efficient spread from person to person
If you have a strain like 1918 that can efficiently infect both the upper and lower respiratory tract, what can happen?
More severe LRT infection
More efficient spread from person to person
What are we worried about with antigenic shift?
Pandemic
How many main avian influenzas have crossed over to infect humans in substantial numbers?
2
Are the 2 avian influenzas that have crossed over to infect humans efficiently spread from person to person?
NO
Do the 2 avian influenzas that have crossed over to infect humans have a high fatality rate?
Yes
Many places worldwide, including the US, are having problems with a slightly different clade (2.3.4.4b) of
______ that is highly pathogenic in poultry
H5N1
What does H5N1 infect?
Wide variety of land and sea mammals
What is infecting US dairy cattle?
H5N1
There are designated HPAI or LPAI-High Pathogenic or Low Pathogenic Avian Influenzas. What is this based on?
Ability of the virus to kill chickens
(NOT humans)
Viral protein that cleaves sialic acid
Neuraminidase
Receptor binding viral protein
Hemagglutinin
