2: Infuenza Flashcards
what questions arose after the 1918 flu?
- why did vaccines against bacteria work?
- why were younger people mostly affected?
- did treatment contribute to death?
what was the worst side effect of the 1976 flu shot?
Guillain-Barre
what questions arose after the 1976 swine flu?
- are the government solutions worse than the problems it creates?
- are vaccines safe?
- why didn’t the 1976 flu become a pandemic?
3 main types of flu, who is infected by each?
A,B,C
- A: humans, animals -> cause pandemics
- B: only humans -> does NOT cause pandemics
- C: mild disease only
what purpose do the 2 flu surface proteins serve?
targets for neutralization by Ab
what are the 2 flu surface proteins, and how many serological types of each are there?
hemaglutinin (H1-H15)
neuraminidase (N1-N10)
how can Influenza A types be further named beyond HxNx?
according to where they were first identified, their lineage number, and the year isolated
mutation rate of flu and why
high mutation rate b/c RNA viruses
describe antigen drift of flu
virus strains change their sequence of H1 and N1 proteins from year to year -> ensures the hosts won’t have neutralizing Abs to future strains
when virus acquires new hemaglutinin and neuraminidase genes
how are the genes of influenza organized?
each gene is encoded on a separate strand of RNA
describe re-assortment of influenza
- when virus envelope is formed, gene segments from different viruses that have infected the same cell can be incorporated into the virus
- allows viruses to easily gain new genes
what one animal is responsible for the origin and spread of influenza A to all other animals?
duck
first major bird flu, what pandemic was it responsible for?
H1N1 -> 1918 Spanish flu
H2N2
-
H3N2
-
next pandemic
-
how long will a strain circulate?
unpredictable - typically one strain that circulates for years causing pandemics
transmission of flu
- large droplets like from sneezing, coughing
- close contact (large drops don’t stay suspended in air)
- contaminated surfaces probably not important
- no chance of getting it from pork or chicken meat
clinical presentation of flu
- fever (most common), headache, myalgia, fatigue
- cough, sore throat and nasal discharge soon follow
- fatigue and weakness may last for weeks
what symptoms/signs are NOT typical features of flu?
- nausea
- vomit
- diarrhea
complications of flu
- viral pneumonia (goes beyond URT into lungs)
- bacterial pneumonia (S. pneumoniae, S. aureus)
- myositis
- rhabdomyolysis
- MI
- encephalitis, encephalopathy
- Reye’s syndrome (actually caused by aspirin given to kids - get hepatic encephalopathy)
things unique to Spanish flu of 1918:
-
- infection started out w/ typical sx, but worsened after several days
- bacterial pneumonia was most common cause of death
- aspirin was given in very high doses
- vaccines made from killed bacteria and injected seemed to have improved mortality
things unique to Bird Flu, H5N1:
-
- affects mostly children and young adults
- very high mortality rates - 60%
- usually a resp illness, but often has diarrhea and neuro sx
- little person-to-person transmission
Avian flu H7N9:
- where?
- who is affected?
- what does it give you?
- transmission?
- primarily occurred in China in early 2013
- elderly more affected
- severe resp illness common
- no evidence of sustained person-to-person transmission
variant H3N2 flu:
-
- found in Indiana at state fairs in 2012, 2013
- cases had close contact with pigs
- appears to be combo of 2009 H1N1 + pig H3N2 strain
- no sustained transmission, mild disease in humans so far
- young kids don’t have Abs, while those 10-14 y/o have some (exposure to virus that circulated in 90s)
mortality during a mild year in US
3000 deaths, mostly in elderly
mortality during severe years and pandemics
about 45,000 deaths, many in kids and young adults
what is the gold standard of diagnosis? problem w/ it?
viral culture, but takes days
what is the best test for diagnosis? problem w/ it?
RT-PCR - highly sensitive and good turn-around, but more expensive
other ways to diagnose?
- rapid Ag tests available, but only moderate sensitivity
- in flu season, sx often enough for diagnosis
older agents for antiviral treatment:
- Amantadine and Rimantadine
- all current strains are resistant to these
newer antivirals for treatment:
nruaminidase inhibitors Oseltamivir (Tamiflu) and Zanamivir
effectiveness of antiviral treatments?
at best reduce sx by 1-2d, but only if given w/i 48h of sx onset
-drugs shown to reduce mortality in 2009 H1N1 outbreak, but not clear if antivirals reduce mortality in other settings
administration of zanamivir
- oral inhalation
- IV also available
what is the new investigational IV drug?
peramivir
how often does a new vaccine need to be made? why?
every year due to antigenic drift in the predominant circulating strains - use educated guesses to figure out which strains will be predominant in the upcoming flu year
how long does it take to make a new vaccine?
9 mo
how are vaccine strains grown?
in eggs - 1 egg makes enough vaccine for 1 shot
-then eggs with virus are purified, virus inactivated with formaldehyde
how is the current vaccine further purified? why?
to have only the HA and N ag’s - called a ‘split’ vaccine - supposedly less side effects
composition of current vaccines
have either:
- two A strains and one B strain (trivalent)
- two A and two B (quadrivalent)
what does the current vaccine have for good measure?
2009 H1N1
composition of 2015 vaccine
H3N2 strain and 1 or 2 B strains
what vaccine is available for people w/ egg allergies?
- cell culture-based vaccine
- also an entirely recombinant vaccine
who is allowed to get the live, attenuated vaccine?
those
advantage of live, attenuated vaccines?
may give better protection, but not proven
vaccine effectiveness
- most effective in children
- in those >65 y/o, not very effective (20-25%)
- vaccines are thought to provide only non-sterilizing immunity, so may still allow infection
- main outcome is prevention or improvement of disease
