Orthomyxoviruses cause ___ and ____ infections
URI and LRI
______ is the most common complication of Orthomyxovirus
Influenza A, B, C
Influenza type ___ is the most virulent
Who does Influenza A infect?
humans and wide variety of animals (Birds, swine, seals, horses)
Who does Influenza B infect?
Who does Influenza C infect?
Humans and Swine
Rarest Influenza is...
Influenza B epidemics are ____ because they ____
Mild, mutate slowly
Most people have antibodies against the ___ strain of Influenza
Types of Influenza that are included in the vaccine
A + B
Types of Influenza that cause human epidemics
A + B
Influenza virus genome (type and segmentation)
ss(-)RNA, segments = 8 for A/B, 7 for C
Influenza surface proteins
M1/2, Neuraminidase + Hemagglutinin
Influenza M1 protein function
forms a layer under the host cell membrane
Influenza Capsid shape
Influenza enveloped or non?
Hemagglutinin functions by...
binding to sialic acid
Hydrolyze sialic acid
Influenza B doesn't have ____
Locations of Influenza replication, assembly, and budding
Replicates in NUCLEUS, assembles in CYTOPLASM, buds at PLASMA membrane
Influenza steps of replication (6)
hemagglutinin BINDS to sialic acid ----- virus is internalized in ENDOSOME ------ endosome ACIDIFIES and capsid and vRNA are released ------ vRNA goes to NUCLEUS ----- mRNA is SYNTHESIZED ---- mRNA TRANSPORTED to cytoplasm for protein synthesis.
Viral RNA polymerase type and subunits
vRNA-dependent RNApol, PA/PB1/PB2
Naked influenza virus assembles in the ____ after undergoing _____
nucleus, secondary transcription
Why does influenza replicate in the nucleus
it doesn't Cap or Polyadenylate it's mRNA (it has to steal the machinery from the host cell)
Incubation time for influenza
Primary complication of influenza
Who is especially at risk for influenza
Women in third trimester of pregnancy ----- elderly -----people with CVD
Primary influenza PNA is further complicated by...
secondary bacterial PNA
Bacterial PNA from influenza... what pathogens?
S aureus, Strep Pneumo, H. Influenzae
Which type of bacterial PNA is most serious?
Sx of Bacterial PNA
elevated WBC, bloody cough, CAVITARY infiltrate on chest Xray
Non pulmonary complications of influenza
swelling of liver and brain, neuro sx and loss of consciousness
Encephalitis is a complication of ________
Who is extremely susceptible to influenza-induced encephalitis
people younger than 7 or older than 55
establish URI by killing epithelial cells (mucus and ciliated) ---- NA cleaves Sialic acid giving access to tissue ---- Desquamation ----- inflammatory cell response ---- Interferon & cytokine responses
Influenza spread by
AIR (droplets) and FOMITES
Influenza is stabile in...
low temp and low humidity
Seasonal Influenza is a result of...
antigenic DRIFT. New strain may require a different vaccine.
Pandemic Influenza is a result of...
antigenic SHIFT of surface proteins. Whole population at risk.
There are __ subtypes of HA and __ subtypes of NA
16 HA 9 NA
Which subtypes (for HA and NA) are known to circulate widely in humans
The only influenza HA strains known to cause pandemics are...
H1, H2, H3
Ag Drift results from
Antigenic shift results from
exchange of a gene segment (REASSORTMENT) -- Due to recombination with another genome of a different antigenic type
Three ways Antigenic shift can occur
Example = Strain jumps through intermediate without changing.... Strain jumps to humans without changing...... or the intermediate gets strain from BOTH humans and bird and reassortment occurs
Hemagglutinin binds to
Human flu HA binds to...
alpha 2,6 sialic acid
Bird flu HA binds to
alpha 2,3 sialic acid
___ have both types of sialic acid receptors, which allows for greater chance of _____ to occur
Humans do, in fact, carry SOME _____, mostly in the trachea
alpha 2,3 sialic acid sequences
Influenza antiviral drugs
Zanamivir, Oseltamivir.... Adamantanes
Zaltamivir and Oseltamivir are active against what?
Influenza A + B
Difference in administration of Zaltamivir and Oseltamivir
Zan = inhalation....... Oselt = Oral
M2 protein --- entry into the endosome & viral release
Influenza vaccine types
Trivalent and Live attenuated
Trivalent flu vaccine is what type?
Trivalent vax made how? How does it protect?
egg grown virus, protects via IgG
Live attenuated influenza vaccine approved for ____ administration to ________ (patients)
nasal........non-pregnant 2 - 49 year olds