Influenza Flashcards
What is influenza?
It is an acute recurring respiratory disease spread by droplet, aerosol, and contact.
Negative sense RNA virus of the family Orthomyxovirdae.
What are negative strand RNA viruses?
-Important causative agents of numerous diseases.
-Have genomic RNAs that are the opposite of the coding “sense” mRNA which is why they are referred to as negative sense or negative strand RNA viruses.
- Only found as enveloped iron particles.
-Major negative strand RNA virus families include:
Paramyxoviruses (measles, virus, respiratory syncytial virus).
Rhabdoviruses (rabies, virus)
Filoviruses (Ebola virus)
Bunyaivurses (Hantavirus)
Arenavirus (Lassa Virus)
Orthomyxoviruses (Influenza virus)
Describe influenza Pandemics through the ages
1580- first described pandemic reported by Hippocrates.
21 have been documented since then
1918: worst pandemic (killed 20-40 million people worldwide).
1918- Spanish flu (originated in Kansas)
1957- Asian flu
1968- Hong Kong flu
1977- Russian flu
2009- H1N1 swine flu
All influenzas are believed to have originated in Asia
What are the symptoms of influenza?
Body or muscle aches
Chills
Cough
Fever
Headache
Sore throat
5-20% of people in the US get flu every year
Can be serious for elderly, newborns, and chronically ill
Influenza genome and particle size
Small genome and just 13 genes!
What is the incubation period of influenza?
Short incubation period of 1-2 days
Describe the flu virus
First isolated in 1930s
First visualized with electron microscope in 1943
Spikes H and N coat the surface of the virus
Describe the HA and NA proteins
HA= Hemagglutinin which is the attachment protein for entry
NA = Neuraminidase which is the cutting protein for exit
Influenza is famous for?
Attacking salicylic acid
How is a cold different from the flu?
Cold is caused by rhinovirus or coronavirus both + strand RNA viruses with a life cycle similar to polio 20-30% of colds are caused by unkown viruses.
Flu caused by influenza the 8 segment strand RNA virus.
Provide a more in depth comparison of cold vs flu
Cold Symptoms
Fever = very rare
Headache = very rare
General aches Pains = slight
Fatigue & Weakness = rare and quite mild
Sneezing, Runny/Stuffy Nose and Sore Throat =almost always
Chest discomfort and coughing = mild to moderate hacking cough
Flu Symptoms:
Fever = 100-102 degrees F comes on quick and lasts 3-4 days
Headache = prominent
General aches and pains = common can be severe
Fatigue and weakness = common, can be severe comes on quick and can last a few weeks
Sneezing Runny/Stuffy Nose and Sore throat = sometimes
Chest discomfort and coughing = common can become severe
Describe severity of influenza in various types of patients.
Fever = worse in children
Symptoms not the same for every age group. Fevers are worse in children.
Explain the classification of Influenza Subtypes
Classified into subtypes based on hemagglutinin (HA) and neuraminidase (NA) membrane surface glycoproteins.
16 HA and 9 NA antigenic forms are known; they recombine to produce influenza subtypes (designated H/N).
What are HA functions?
Functions in viral attachment to host cells.
-attaches to galactose-sialic acid receptors on the host cell.
-defines viral tropism (which tissues virus attacks).
-major surface epitope seen by the immune system.
What are NA functions?
functions by cleaving viral particles from host cells
-allows for virion release (continued spread of virus particles).
What do antivirals do?
inhibitors of neuraminidase
If you developed a drug that bound to and cleaved HA what do you think its direct effect would be on influenza pathogenesis?
Virus would be unable to infect cells.
Describe the genome plasticity of flu viruses
Important feature is its high frequency of genetic changes
What is antigenic drift?
-Due to accumulation of mutations in a strain within an area.
-Often the result of point mutations that lead to amino acid substitutions.
What is antigenic shift?
due to reassortment of genomes when two different strains of flu viruses (from humans and animals) infect the same cell and are incorporated into a single new capsid.
If an avian influenza develops a series of point mutations that now allows the virus to infect human cells this is called?
Antigenic drift
What are type A flu strains?
Found in humans, ducks, chickens, pigs, whales, horses, seals.
Can cause yearly pandemics (can lead to more antigenic shift).
What are type B flu strains?
Found typically only in humans
Can cause yearly epidemics
What are type C flu strains?
Causes mild respiratory illness (does not lead to epidemics).
What are current flu A subtypes found in the US?
H1N1
H3N2
What happens if a pig is infected with 2 different subtyepes of flu virus simultaneously?
If virus winds up in the same host cell they should exchange genetic material (RNA) resulting in a new variant.
Why was the 1918 influenza pandemic unique?
More death in young healthy people
Provoked health immune system.
Describe the “flu shot”
an inactivated vaccine (containing killed virus) that is given with a needle usually in the arm.
-Flu shot is approved for use in people older than 6 months including healthy people and people with chronic flu.
Describe the “flu shot”
an inactivated vaccine (containing killed virus) that is given with a needle usually in the arm.
-Flu shot is approved for use in people older than 6 months including healthy people and people with chronic medical conditions.
Describe the nasal spray flu vaccine
a vaccine made with live weakened flu viruses that do not cause the flu.
-sometimes called LAIV for live attenuated influenza vaccine or FluMist.
-approved for use in healthy people 2-49 years of age who are not pregnant.
-grows well in cold but not at body temperature.
What was a bad flu season and how effective is the flu shot at fighting off H3N2 strain of the virus?
More people were hospitalized with the flu in 2018 than experts recorded.
The flu shot is about 10-20% effective at fighting off the H3N2 virus.
