Respiratory Viruses and atypical respiratory pathogens

Question 1

Respiratory tract

Answer 1

Begins with inhalation
Some viruses are restricted to certain areas
Lower respiratory and upper r tract

Question 2

Types of infection - surface

Answer 2

Surface

• local spread - stay localised to epithelial layer
• short incubation

Question 3

Types of infection - systemic

Answer 3

Spreads from mucosal site of entry to other site in body
returns to surface for final shelling
longer incubation of a few weeks e.g MMR

Question 4

Professional invaders

Answer 4

Infect healthy resp tract

Question 5

Secondary invaders

Answer 5

Infect compromised tract

Question 6

Infections of nasopharynx

Answer 6

Rhinitis/sinusitis - common cold

Question 7

Rhinitis and sinusitis =

Answer 7

common cold
spread by aerosol
not systemic

Question 8

Lytic infection

Answer 8

Virus adheres to ciliated epithelium
Enters cells and replicates inside cells and spread
Inflammatory response results

Question 9

Common cold virus examples

Answer 9

Rhinovirus, influenza, adenovirus

Question 10

Adenovirus

Answer 10

Pentagonal capsule
Resistant to desiccation
Adhesins on end of penton fibres attach to cells
dsDNA

Question 11

Pharyngitis and tonsillitis

Answer 11

70% caused by viruses
Common complication of common colds due to surrounding infections
complication of common colds

Question 12

Mumps

Answer 12

Paramyxovirus
airborne spread during school
Most children vaccinated

Question 13

Laryngitis and tracheitis

Answer 13

Caused by parainfluenza, influenza and adenovirus
Burning pain in larynx
Obstructed easily in children

Question 14

Bronchitis and Bronchiolitis

Answer 14

Viral causes - coronavirus, rhinovirus 
Smoking related 
atypical pathogens e.g pneumoniae
Secondary infections 
75% caused by RSV

Question 15

Respiratory syncytial virus
Mechanism
Signs in infants

Answer 15

Aerosol spread
Large fused cells created 
Outbreak in winter 
causes 75% of bronchitis 
Cyanosis, cough, Rapid RR, pneumonia 
Some antivirals are used - ribavirin 
Some antigens on surface change seasonally therefore definite cure is hard to come across

Question 16

Influenza virus
Transmission
Mechanisms

Answer 16

Aerosol droplet
Initial infection involves attachment of virus to silica acid receptors on epithelial cells via viral HA protein
1-3 days - liberated cytokines result in systemic chills, malaise, fever and muscle aches, runny nose and cough
1 week recovery
Some develop pneumonia and bronchitis
Secondary invaders can cause lethal infections: pneumococci, staph

Question 17

Influenza structure

Answer 17

Two surface glycoproteins
HA haemaglutinin
NA neuraminidase

Question 18

HA
types
mechanism

Answer 18

16 avian and mammalian
only 3 human adapted
adheres to sialylated surface receptors and internalisation
HA binds silica acid receptors on epithelial cell surface
major source of antigenic variation

Question 19

NA
type
mechanism

Answer 19

9 known serotypes and 2 human adapted

neuraminidase and M2 proton ion channel- involved in release from the cell into the resp tract..

Question 20

Three types of influenza

Answer 20

A - yearly epidemics and occasional serious worldwide - reservoirs in birds and pigs
B - yearly epidemic
C - minor resp illness

Question 21

Antigenic drift

Answer 21

Small point mutations in H antigen and N antigen which accumulate in popn
Result in new variant viruses which reinfect
Mutations occur in antigenic parts of molecule to prevent antibody binding

Question 22

Flu vaccines

Answer 22

Strains grown in hen eggs
contain one H3N2, H1N1 and one B strain
Don’t cover pandemics as they come from unexpected strain

Question 23

Antigenic shift

Answer 23

Less common
Major shift in viral composition
Gene reassortment –>. new HA and NA types

Question 24

Antigenic shift mechanism

Answer 24

Infection of human animal with human and other influenza virus
Reassortment of genes due to recombination with existing human virus
Spread through immunologically naïve popn
pandemic

Question 25

Combatting an epidemic
Info required
Issues with antiviral drugs

Answer 25

Which virus
Antiviral drugs
Resistance is an issue

Question 26

Pneumonia

Mechanism

Answer 26

Organisms <5mm entering alveoli

Secondary to preceding damage e.g cystic fibrosis or influenza

Question 27

Atypical pneumonia

Answer 27

Less severe
Most resistant to penicillin
Mainly caused by chlamydophila, legionella
AIDS associated also

Question 28

Mycoplasma pneunomiae features and mechanism

Answer 28

Small bacterium
No peptidoglycan layer therefore resistant to penicillin
efficient binding to cilial epithelial cells via special cytadherence organelles rich in a cytadhesin for silica acid rich glycolipids

Question 29

Chlamoydophila pneumonia features

Answer 29

Small pathogen 
intracellular growth 
no peptidoglycan
flu like illness 
detected by indirect methods

Question 30

Legionnaires disease

Answer 30

legionella pneumophila
no human-human transmission
Air-con, spa baths, hot air heating
hospitals, hig

Question 31

Legionnaires disease

Answer 31

legionella pneumophila 
no human-human transmission 
Air-con, spa baths, hot air heating 
hospitals, high rise blocks 
intracellular invader of phagosomes and lung cells

Question 32

Legionella pneumophila

Answer 32

Motile

Cultured on buffered charcoal yeast extract

Question 33

Atypical pneumonia

Answer 33

NOT treatable by penicillin
NOT caused by S pneumoniae
symptoms generally less severe