Influenza Virus and Vaccines Flashcards
Describe the structure of Orthomyxovirus
negative sense, segmented RNA, helical, Enveloped
What are the types of Influenza?
Influenza A
Influenza B
Describe Influenza A
-Infects Humans, swine, and avians
-Is capable of antigenic drift and shift
-Combines hemagglutinin 1,2, or 3 with neuraminidase 1 or 2.
-Is the cause of most epidemics and all pandemics
Describe Influenza B
-Infects humans
-Genetic drift is the genetic change that is most problematics
-Can result in reinfection and changing the vaccine, rare epidemics, and no pandemics
What does Antigenic Drift result in?
-Small changes in the virus
-The most critical mutations are in the hemagglutinin (HA) envelope protein
-Mutations in HA have the potential to allow the virus to escape neutralizing antibodies
-*Antigenic drift in HA will enable the virus to reinfect people and is the reason to change the flu vaccine
What is Antigenic shift?
-Large changes
-Is the swapping of viral RNA segments between human and avian, or human and swine, or all three viruses
-This mixing can sometimes lead to a vastly new virus that can cause a pandemic
How is Influenza spread?
Person to person via respiratory droplets and fomites
How is influenza killed?
Influenza is an enveloped virus and is killed with detergents, heat, acid, and drying
Most of the deaths caused by influenza are by people of what age group?
65+
-A large number of people are infected each year with thousands of hospitalizations. Most hospitalizations occur in people with underlying health conditions, but previously healthy adults and children are hospitalized and some die yearly
A ______ strain of influenza will become the new sessional influenza until supplanted by a new pandemic strain
pandemic
What type of infection is influenza and what it its incubation time?
Local infection; short incubation time
How long to influenza symptoms last?
Symptoms last 2-3 days and can be as long as 5. Most recover, but some lack strength and energy for several weeks; a cough can linger
When do adults shed the virus? Children?
-Adults shed the virus one day before symptoms to 5-7 days after
-Children can shed up to 10 days after symptoms
What are about 1/3 of influenza deaths due to?
-Secondary bacterial pneumonia (Pneumonia caused by influenza is rarer but is generally worse and has a high fatality rate.)
-Other causes are due to underlying health problems such as heart disease or pulmonary disease
The viral Hemagglutinin binds to _______
sialic acid
The _____ linkage is the type human influenza virus bind.
alpha2-6
-It is present in the upper respiratory tract at high levels and only in the lower respiratory tract at low levels
Bacterial pneumonia is most prevalent in people with underlying lung problems, but even the healthy can get secondary bacterial infections. List the ways how.
1) Killing air epithelial cells make it easier for bacteria to bind in the airway
2) Influenza can kill alveolar macrophages that help prevent bacterial infection
3) Airway edema and dead cells create a nutrient-rich environment for bacterial growth
4) The viral neuraminidase inactivates some innate antimicrobials that might help kill bacteria and exposes bacterial attachment sites
___________ is a detergent disrupted inactivated virus. Just the HA and NA are isolated and put in the vaccine
Inactivated Influenza Vaccine (IIV)
_________ contains a cold-adapted influenza virus containing the HA and NA in the inactivated vaccine
Live attenuated influenza vaccine (LAIV)
________ contains an entirely recombinant HA protein grown in cell culture
Subunit vaccine (RIV)
All of the influenza vaccines are ______
quadrivalent
What does the quadrivalent vaccine contain?
Two strains of influenza A and two strains of influenza B
How do they pick the vaccine strain for influenza?
It takes time to make the vaccine. This means the vaccine strains must be picked well before the flu
season. They do this by seeing what strains of influenza are prevalent in other parts of the world. These viruses will go into our seasonal influenza vaccine.
Protection from influenza infection is achieved ________ after vaccination
2 weeks
List the neuraminidase inhibitors
Zanamivir and Oseltamivir
What do Zanamivir and Oseltamivir do?
-They prevent the budding and release of the virus.
-It must be used within 2-3 days of infection to have a maximal effect
What is the new drug used to treat influenza?
Baloxzvir
What is the function of Baloxzvir?
-It is a cap-dependent endonuclease inhibitor
-It block the ability of the virus to ‘snatch caps’ and transcribe viral mRNA
-It seems to be as effective as neuraminidase inhibitors
-It should be used within 2-3 days of infection for effectiveness
Describe the 1918 flu epidemic
1) Infected 1/3 to 1/2 of the world’s population
2) Fatality rate >2.5%
3) It had a W-shaped mortality curve, meaning more deaths in the 18-40 year age than normal for influenza
Avian strains recognize _______ linkages, which are present more in the lower respiratory tract
alpha 2,3 Sialic acid linkages
-This makes for a more severe LRT infection but also less spread from person to person
Human strains recognize _________ linkages present at higher levels in the Upper Respiratory Tract
alpha 2,6 Sialic acid linkages
-This alpha 2,6 Sialic acid usage means there is less chance of LRT infection but much more efficient person-to-person spread
What would happen if you have a strain like the 1918 that can efficiently infect both the upper and lower respiratory tracts?
There can be severe LRT infections and efficient person-to-erson spread
A _______ is present in avian flu and the 1918 influenza but not in human influenza
virulence factor
Another necessity in a pandemic strain is _________ in the population to the new influenza virus
little immunity
What is the “Bird” Flue designated as? What is this based on?
-Designated HPAI or LPAI-High Pathogenic or Low Pathogenic Avian Influenza
-Based on the ability of the virus to kill chickens, not humans
What are the two main avian influenzas that have crossed over to infect humans?
H5N1 and H7N9
What is H5N1considered?
HPAI and can cause devastation in the poultry industry
What are the two strains of H7N9
LPAI and HPI
Is either H5N1 or H7N9 spread person-to-person?
Neither virus is efficiently spread from person-to-person
