lecture 27- viral infections of the respiratory tract Flashcards
what virus causes influenza
structure and special properties
- orthomyxovirus (related to parinfluenza virus and paramyxovirus)
- segmented (important in it being able to mutate and change)
- ssRNA
- enveloped
- contains hemagglutinin and neuraminidase
what do hemagglutinin do? what does neuraminidase do?
hemagglutinin- agglutinates RBCS and allows for attachment
neurominidase- cleaves sialic acid, viron release, viron spread
= both are antigenic
antigenic DRIFT
epidemiologically significant changes occur every how many years?
- small changes in H and N (point mutations) made by influenza virus that allows a change in hemoagluttinin and neurominidase in order for it NOT to be recognized by the immune system
- epidemiologically significant changes ever 2-3 yrs
Antigenic SHIFT
-large changes in H and N driven by REASSORTMENT of two viruses -leads to change in neuromididase and hemagluttinin = swapping antigenicity
-co-infection of the same cell
RISK FOR PANDEMICS
what are the three types of influenza viruses? which one is the only one that causes genetic shift? which one does not have a vaccine because the symptoms are so mild? list the viruses in order of severity of symptoms. which virus type has the highest host range?
- a,b,c
- A causes genetic shift
- C is the one without a vaccine
- A, B, C
- A has the highest host range
how do you name a virus and what hemagluttinin and neurominidase numbers infect humans?
- serotype (A-C)
- where it was isolated (state)
- isolate number/year
- Hemagluttinin number (1-3)
- neuraminidase (1-3)
what made the 2009 influenza A (H1N1) so virulent
-it was multiple viral reassortments (genetic shift) of an avian, swine and human virus
what are deciding factors for treatment of influenza virus with antivirals
- if the person does not have risk factors- then you MAY treat with antivirals within 48 of initial onset but should get better in 72 hrs
- if the person has risk factors, treat with antivirals no matter what
what are some ion-channel blocker antivirals used? what are they protective against? how do they work?
- rimantadine and amantadine
- protective against influenza type A- but current influenza type A is resistant
- the prevent replication prior to genome release
how do neuraminidase inhibitors work? what are they protective against? special instructions?
what are the three types of neurominidase inhibitors and their route?
- neuraminidase inhibitors inhibit viron release and spread (fights against influenza virus)
- protective against influenza A and B
- for UNCOMPLICATED influenza- must be before 48 hr to reduce symptoms and duration
- 3 types: Zanamivir (oral inhalation), oseltamivir (oral)- tamiflu, peramivir (IV)
what are the three types of vaccines
- inactivated- comes as intradermal (18-65) and IM- IM is good for anyone over 6 mo old
- live attenuated- intra-nasal- for healthy, nonpreg, 2-49 y.o.
- recombinant influenza- HEMOGLUTTININ PROTEIN GIVEN INTRAMUSCULARLY (18-49)
hwo are virus vaccines made?
- classic method- via embryonated chicken eggs -takes long!
- novel method- starts from eggs- put into mammalian cells- grow quick, reduced risk for people with egg allergies
if your patient has an egg allergy, what type of vaccine should be considered for them?
-recombinant influenza vaccine because it is prepared using insect cells: baculovirus made to express hemogluttinin (expression vector system technology)
egg free system!
what do trivalent and quadravalent vaccines protect for?
Trivalent -2 Influenza A viruses and 1 B
quadravalent- 2 A, 2 B
when do you vaccinate? who gets vaccinated first? what’s special to note about kids younger than 9 yo getting the vaccine for the first time
- ideally 2-4 months before viral infection
- immunosuppressed people and healthcare workers
- must get 2 times
