3. Hospital acquired infections pre-session

Question 1

What is meant by a reservoir?

Answer 1

Reservoir of an infectious agent is the habitat in which the agent normally grows, and multiplies

e.g.- Humans, animals and the environment

Question 2

Give some examples of diseases without intermediaries

Answer 2

STDs, measels, mumps and streptococcal infection

Question 3

Why was smallpox eradicated after the last human case was identified and isolated?

Answer 3

Humans were the only reservoir for the smallpox virus

Question 4

What is meant by a carrier when referring to a human?

Answer 4

Someone who is with inapparent infection but is capable of transmitting the pathogen to others

Question 5

What is the difference between a carrier and a vector?

Answer 5

A carrier is infected even if they are asymptomatic

Whereas a vector is not infected with the disease even if they have it on them

Question 6

What are the three different types of Carriers?

Answer 6

Incubatory - Those who can transmit the agent during the incubation period and before clinical illness begins

Convalescent - Those who recovered from illness but remain capable of transmitting to others

Chronic - Those who continue to harbour causative agent for months of even years after initial infection

Question 7

What is meant by zoonosis?

Answer 7

Infectious disease that is transmissible under natural conditions from vertebrae animals to humans

Question 8

Give five ways in which a pathogen can leave a host

Answer 8

Respiratory tract

Urine

Feces

Crossing placenta from mother to foetus

Cuts or needles in skin

Question 9

Describe and explain the two modes of Direct Transmission

Answer 9

Direct contact - Skin-to-skin, kissing, and sexual intercourse

Droplet spread - Direct spray from short range aerosols produced by sneezing, coughing, or even talking

Question 10

Describe the three modes of Indirect Transmission

Answer 10

Airborne transmission - Occurs when infectious agents are carried by dust or droplet nuclei suspended in air

Vehicles - Food, water, blood and fomites (inanimate objects)

Vectors - Mosquitoes, fleas and ticks may carry infectious agent through purely mechanical means

Question 11

Give 3 examples of non-specific factors that defend against infection

Answer 11

Skin

Mucous membrane

Gastric acidity

Question 12

How could Vehicleborne transmissions be reduced?

Answer 12

Elimination or decontamination of vehicle

Question 13

How could airborne transmissions be reduced?

Answer 13

Modifying ventilation, or air pressure

Filtering or treating the air

Question 14

How could vectorborne transmission be reduced?

Answer 14

Controlling vector population, such as spraying to reduce mosquito population

Question 15

Give 2 examples of interventions that aim to increase a host’s defence

Answer 15

Vaccinations promote development of specific antibodies that protect against infection

Prophylactic use of antimalarial drugs, prevents infection from taking root

Question 16

• What kind of intervention might prevent a pathogen from encountering a susceptible host?

Answer 16

Herd immunity - Suggests that if high enough proportion of individuals in a population are resistant to an agent, then those few who are susceptible will be protected by resistant majority, since pathogen will be unlikely to ‘find’ the few susceptible individuals