Influenza

Question 1

What is the structure of influenza?

Answer 1

Spherical, envoloped with segmented negative strand of RNA

Has 2 surface antigens H and N

Question 2

Whate are the 3 types of influenza?

Answer 2

A- humans and animals

• antigenic shift and drift
• causes pandemics

B-humans

• antigenic drift
• older adults

C-humans and birds

• antigenic drift
• mild disease

Question 3

What does surface antigen H do?

Answer 3

Bins to cell of infected person

Question 4

What does surface antigen N do?

Answer 4

Releases virus from host cells surface

Question 5

How is influenza transmitted?

Answer 5

Via resp route;

• small particle arosols
• larger particle droplets
• viral partcles landing on surfaces

Question 6

How does influenza enter the human host cell?

Answer 6

Sialic acid on glycoprotein (of host) NANA residue binds to H antigen on influenza

NANA acts as receptor for receptor mediated endocytosis

Question 7

What are the main symptoms of influenza?

Answer 7

Fever
Headache 
Dry cough 
Sore throat 
GI (more in kids)
Fatigue

Question 8

What are the main complications of influenza?

Answer 8

Meningitis 
Otitis media (ear infection) *
Croup*
Sinutis 
Pneumonia 

*more in children

Question 9

How is flu diagnosed in hospitals?

Answer 9

Nasopharyngeal swap

Either rapid test (tell if type A or B)
PCR test in lab

Question 10

How does influenza leave host cells?

Answer 10

1) H antigen binds to NANA

2) N antigen binds to NANA and cleaves it away from H allowing virus to leave

Question 11

How can influenza be treated?

Answer 11

Antivirals- inhibit uncoating so not uptaken
-for type A

Neuraminidase- inhibit relases from infeted cells by blocking N antigen
-for type A and B

Prevention-formalin-inactivated vaccine
-live attenuated vaccine (nasal spray)

Question 12

What is antigenic drift?

Answer 12

Minor changedd in genes of flu virus that occour gradually over time

Changes in N and H

Causes seasonal epidemics

Question 13

Why does genetic drift occour?

Answer 13

Flu constantly replicating (life cycle 6 hours)

RNA polymerases have high error rate

Lack of proof reading so mutations arise

Question 14

What is antigenetic shift?

Answer 14

Major changes in genes of flu virus that occour suddenly when 2 or more strains combine within a host (animal)

Causes epidemics and pandemics

New subtype of influenza

Question 15

How does the flu kill?

Answer 15

Immune system over reacts- T cells attack and destroy tissue where virus present

Opportunistic secondary infection