Influenza Flashcards
what type of virus is influenza
ssRNA, enveloped, helical nucleocapsid, 8 segment genome
surface antigens on influenza
A or B, H (hemagglutinin), and N (neuraminidase
antigenic drift
minor antigenic changes based on random mutations of either hemagglutinin or neuraminidase, cause epidemics
antigenic shift
reassortment of segments of viral genome which lead to a new virus to which the population has no immunity, cause pandemics, more deadly
why did mostly young people get effected by H1N1 in 2009
the H1N1 flu subtype had previously come in the early 1920s (Spanish flu) and the 70’s (Russian flu), so a lot of the older population had already developed immunity to it
how do viruses get deposited on respiratory tract
inhaled, attach to epithelium, penetrate columnar epithelial cells
what safeguards are in place to prevent the attachment of pathogens to the epithelial lining of the respiratory tract
specific secretory antibodies IgA, nonspecific mucoproteins, mechanical ciliary action
viral infection leads to viral replication leads to cell death leads to
release of the virus, initiating infection of the adjacent cell
incubation period of influenza virus
1-4 days
illness duration of influenza virus
2-5 days
viral shedding
1 day before symptoms, for a total of 6 days
transmission of influenza virus
large droplet, close contact with infected person, can only travel 6 feet, possible small respiratory or from fomites
fomites
inanimate objects that serve as a vector for infection
clinical symptoms of influenza
fever, chills, headaches, myalgia, malaise, anorexia, dry cough, sore throat, nasal congestion/discharge
length of systemic system persistance
3 days, typical duration of fever
pulmonary complications of influenza
pneumonia, croup, COPD
non-pulmonary complications of influenza
myositis, cardiac (toxic shock), guillain-barre (influenza A), transverse myelitis, encephalitis, Reye syndrome (aspirin in children)
real-time PCR test
most sensitive and specific, but low availability and long wait for results
RA rapid antigen detection
used in ER, takes 10-20 minutes, but only has a sensitivity around 60%, so you get a lot of false negatives; if you get a negative, you should probably double check with RA
M2 blockers
work by blocking uncaring by amantadine
neuraminidase inhibitors
prevent the release of the virus through exocytosis by oseltamivir (tamiflu) and zanamivir
early antiviral treatment can
shorten illness/fever duration, reduce death, shorten hospitalization in children
when to start antiviral treatment
within 48 hours of symptom onset
who do you give antiviral treatment as early as possible to when influenza is suspected
hospitalized patients, severely ill patients at high risk for complications, complicated/progressive comorbidities
what drugs are the M2 blockers
rimantadine and amantadine
what drugs are the neuraminidase inhibitors
oseltamivir, zanamavir, peramivir
rimantidine
blocks viral uncaring by blocking M2 proton channel, oral administration, treats influenza A, some GI intolerance and CNS effects
amantidine
blocks viral uncaring by blocking M2 proton channel, administered orally, treats influenza A
what virus strain do M2 blockers prevent
influenza A
Oseltamivir
tamiflu, pro-drug activated in gut and liver, inhibit neuraminidase, administered orally, treats influenza A and B, well-tolerated with some nausea and vomiting
Zanamivir
relenza, inhaled drug, inhibits neuraminidase, treats influenza A and B, bronchospasms occur in asthmatics, nausea, and diarrhea
Peramivir
Rapivab, IV admin, inhbiits neuraminidase, treats influenza A and B, causes diarrhea
when to use influenza prophylaxis
close contact with person who has confirmed/probably/suspected influenza IF high risk for complication, IF <48 hours since last contact, and IF contact within 24 hours of infections period (fever subsiding)
definition of “close contact”
cared for/lived with person with flu, high likelihood of contact with large droplets/body fluids, talked fact-to-face, intubated them, etc.
which populations qualify for the high dose vaccine
adults >65, kids 6-8 months require 2 doses if it’s their first vaccine, and high risk individuals i.e. HIV positive, will get high-dose vaccine
common cold viruses
rhinovirus and respiratory syncytial virus
RSV is significant because
it is the most common cause of death from respiratory illness in young children, and the leading cause of death from respiratory illness in those >65
if the vaccine matches the circulating strain well, what’s your risk reduction for developing flu that will lead to a dr. appointment
50% risk reduction
relative measure of effect
1-odds ratio x 100, so what are the odds those with the flu were vaccinated/what are the odds those without the flu were vaccinated
1-that x 100
number needed to treat
well matched: 37, not well matched: 77
hemagglutanin
binds sialic acid and promotes viral entry into the host cell
neuraminidase
promotes progeny virion release
