Influenza

Question 1

What is influenza?

Answer 1

It is an acute recurring respiratory disease spread by droplet, aerosol, and contact.
Negative sense RNA virus of the family Orthomyxovirdae.

Question 2

What are negative strand RNA viruses?

Answer 2

-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)

Question 3

Describe influenza Pandemics through the ages

Answer 3

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

Question 4

What are the symptoms of influenza?

Answer 4

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

Question 5

Influenza genome and particle size

Answer 5

Small genome and just 13 genes!

Question 6

What is the incubation period of influenza?

Answer 6

Short incubation period of 1-2 days

Question 7

Describe the flu virus

Answer 7

First isolated in 1930s
First visualized with electron microscope in 1943
Spikes H and N coat the surface of the virus

Question 8

Describe the HA and NA proteins

Answer 8

HA= Hemagglutinin which is the attachment protein for entry
NA = Neuraminidase which is the cutting protein for exit

Question 9

Influenza is famous for?

Answer 9

Attacking salicylic acid

Question 10

How is a cold different from the flu?

Answer 10

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.

Question 11

Provide a more in depth comparison of cold vs flu

Answer 11

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

Question 12

Describe severity of influenza in various types of patients.

Answer 12

Fever = worse in children
Symptoms not the same for every age group. Fevers are worse in children.

Question 13

Explain the classification of Influenza Subtypes

Answer 13

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).

Question 14

What are HA functions?

Answer 14

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.

Question 15

What are NA functions?

Answer 15

functions by cleaving viral particles from host cells
-allows for virion release (continued spread of virus particles).

Question 16

What do antivirals do?

Answer 16

inhibitors of neuraminidase

Question 17

If you developed a drug that bound to and cleaved HA what do you think its direct effect would be on influenza pathogenesis?

Answer 17

Virus would be unable to infect cells.

Question 18

Describe the genome plasticity of flu viruses

Answer 18

Important feature is its high frequency of genetic changes

Question 19

What is antigenic drift?

Answer 19

-Due to accumulation of mutations in a strain within an area.
-Often the result of point mutations that lead to amino acid substitutions.

Question 20

What is antigenic shift?

Answer 20

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.

Question 21

If an avian influenza develops a series of point mutations that now allows the virus to infect human cells this is called?

Answer 21

Antigenic drift

Question 22

What are type A flu strains?

Answer 22

Found in humans, ducks, chickens, pigs, whales, horses, seals.
Can cause yearly pandemics (can lead to more antigenic shift).

Question 23

What are type B flu strains?

Answer 23

Found typically only in humans
Can cause yearly epidemics

Question 24

What are type C flu strains?

Answer 24

Causes mild respiratory illness (does not lead to epidemics).

Question 25

What are current flu A subtypes found in the US?

Answer 25

H1N1
H3N2

Question 26

What happens if a pig is infected with 2 different subtyepes of flu virus simultaneously?

Answer 26

If virus winds up in the same host cell they should exchange genetic material (RNA) resulting in a new variant.

Question 27

Why was the 1918 influenza pandemic unique?

Answer 27

More death in young healthy people
Provoked health immune system.

Question 28

Describe the “flu shot”

Answer 28

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.

Question 28

Describe the “flu shot”

Answer 28

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.

Question 29

Describe the nasal spray flu vaccine

Answer 29

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.

Question 30

What was a bad flu season and how effective is the flu shot at fighting off H3N2 strain of the virus?

Answer 30

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.