Chapter 19: Respiratory System Infections-Part 2

Question 1

Influenza type A incubation period

Answer 1

Short, averaging two days

Question 2

Initial symptoms of seasonal influenza

Answer 2

Headache, fever, muscle pain, dry cough - abate within a week

Question 3

Influenza B and C viruses..

Answer 3

Only circulate in humans

Question 4

Influenza type A virus structure

Answer 4

Negative sense RNA, H and N spike proteins, enveloped

Question 5

Negative sense RNA

Answer 5

Segments of single stranded RNA individually surrounded with nucleocapsid proteins

Question 6

Influenza A virus causative agent

Answer 6

Belong to orthomyxovirus

Question 7

Orthomyxovirus genome

Answer 7

Divided into 8 gene segments (2 code for spikes)

Question 8

H spike

Answer 8

Hemagglutinin (H1-H16)

-Aids in attachment

Question 9

Which H spike viruses circulate in humans?

Answer 9

Only H1, H2 and H3 viruses

Question 10

N spikes

Answer 10

Neuraminidinase (N1-N9)

-Cleaves H protein to allow fusion of viral and cellular membranes (entry into the cell)

Question 11

N spikes require cellular enzyme ______ to facilitate infection

Answer 11

Trypsin

Question 12

Influenza A transmission cycle

Answer 12

• Wild birds (they do not get sick)
• Transmission to domestic fowl
• Adaption / reassortment with swine influenza viruses
• Transmission to humans

Question 13

If a strain comes without swine combination..

Answer 13

Bird flu: much more serious

Question 14

Seasonal influenza virus acquired through..

Answer 14

Inhalation of infected respiratory secretions

Question 15

First step in influenza pathogenesis

Answer 15

Virus attaches to host cells with H spikes

-Envelope fuses, viral replication occurs

Question 16

After viral replication..

Answer 16

Mature viruses bud from host cell (allows mature virus to pick up envelope)

Question 17

After viruses bud from cell,

Answer 17

Infected cells die and slough off

Question 18

How does host immunity quickly control viral speed?

Answer 18

Anti-HA neutralizing IgG

Question 19

How many Americans are infected each year with influenza?

Answer 19

Hundreds of thousands or millions

Question 20

On average, about ______ Americans, mostly elderly and very young children, die from influenza each year

Answer 20

30,000

Question 21

Pandemics of influenza occur..

Answer 21

Periodically

Question 22

Pandemics have..

Answer 22

Higher than normal morbidity

Question 23

Antigenic drift

Answer 23

Consists of amino acid changes in spikes (point mutations)

Particularly hemagglutinin

Question 24

Antigenic shift

Answer 24

Represent more dramatic changes

Question 25

Antigenic shift: virus strains are drastically ________ different from previous strains, particularly in the _________

Answer 25

Antigenically

Hemagglutinin

Question 26

Antigenic shift: new virus comes from..

Answer 26

Genetic re-assortment (occurs when two viruses infect a cell at the same time)

Question 27

Seasonal influenza prevention

Answer 27

Vaccine can be 80-90% effective

Question 28

A new vaccine is required every year because of..

Answer 28

Antigenic drift

Question 29

Antiviral medications are __ to ___ % effective

Answer 29

70-90

Question 30

Antiviral medications for influenza include..

Answer 30

Amantadine, rimantadine, and Tamiflu

Have to be taken early