chain of infection

Question 1

Classification of human pathogens

Answer 1

Transmissibility = spread

Virulence = severity of disease, ability to cause disease

Vaccine effectiveness

Diagnostic testing

Question 2

Superspreaders

Answer 2

associated with higher than normal amount of infectious material through exhaled breath/skin

Question 3

3Cs of virus spreading

Answer 3

• Closed settings with poor ventilation (1-3l/s/person)
• Closed contact
• Crowding

Question 4

ideal ventilation conditions

Answer 4

• To provide 10 air changes per hour in the surgery
• Rubber dam
• High volume aspiration
• portable room air cleaners with HEPA and UV air disinfection

Question 5

maintain CO2 concentration below?? in clinic ventilation

Answer 5

800ppm

Question 6

ID50

Answer 6

infectious disease 50

number of mircobes needed to cause infection

Question 7

influenza ID50

Answer 7

 Influenza = <10

Question 8

virulence factor

Answer 8

ability of the microbe to cause disease

examples are exotoxins and endotoxins

Question 9

are LPS exo or endotoxins

Answer 9

endotoxins

Question 10

podromal phase

Answer 10

asymptomatic phase
measles mumps chicken pox

Question 11

healthy carriers

Answer 11

peoplewho are infected but show no clincial signs

Question 12

incubation period

Answer 12

the time between contamination and the development of symptoms

Question 13

Asymptomatic carrier =

Answer 13

infected person with no clinical evidence of disease

Question 14

Colonisation vs infection

Answer 14

 Colonisation is the presence of microorganism in a host with growth and multiplication but without any overt clinical expression at the time the microorganism is isolated

do not treat colonisation

Question 15

R0

Answer 15

Basic reproduction number

the number of cases one case generates on average over the course of its infectious period

Question 16

R0<1 =
R0>1 =

Answer 16

R0<1 = infection will die out in the long run

R0>1 = infection will be able to spread in a population

Question 17

Factors affecting R0

Answer 17

• Duration of infectivity
• Infectiousness
• Number of susceptible people

Question 18

flu R0 value
covid R0 value

Answer 18

flu 1.3
covid 2.4
measles 15-18

Question 19

difference between airborne vs droplets

Answer 19

– Airborne (aerosols) => less than 5 microns, respi pathway
- Droplets => more than 5 microns => non respi pathway

Question 20

Why does particle size matter?

Answer 20

tells you what ppe to use

• airborne = FFP3 mask, gown, fallow time
• droplet = fluid resistant surgcial mask, ppe

Question 21

how long can a 5um particle stay in the air

Answer 21

30min

Question 22

what factors affct the survival of the viral particle in mode of transmission?

Answer 22

 temperature
 humidity
 ph
 ventilation
 airflow
 salinity (can buffer and protect virus)
 surface material (Copper is good)
 UV
 Size
 surfaces (porous surfaces are better)
 Viral load

Question 23

Portal of entry virus examples for each
respi tract
gastrointestinal tract
open wounds
sharps
sexual contact

Answer 23

respi tract – influenza virus
gastrointestinal tract – salmonella or norovirus
open wounds – S. aureus
sharps – BBV
sexual contact – HIV

Question 24

how does influenza virus enter the body

Answer 24

• aerosols
• inhalation
• direct contact droplets
• indirect contact settle particles, touching face

Question 25

why should dentists take the flu vaccine?

Answer 25

protect urself ur pateitns family and collagues

Question 26

Susceptible host

Answer 26

• weak immune
• drugs that impair host defencs
• breaks in skin
• medical devices
• unable to fight infection