Transmission Of Infection

Question 1

What causes infection?

Answer 1

Microorganisms- some cause infection some don’t. Have them on parts of the body( norm flora)
However these can cause illness if spread to other areas of the body- bacteria from bowel enter bladder

Question 2

How do we become infected with microorganisms?

Answer 2

Deposited on skin from other individuals or from inanimate environment ( formites) = transient
These can be removed or destroyed by frequent hand washing

Question 3

What is a reservoir?

Answer 3

A host that carries a pathogen without injury to itself and serves as a source of infection for other host organisms.
Example unclean commode can be contaminated with microorganisms that cause diarrhoea

Question 4

What must microorganisms have to cause infection?

Answer 4

Point of entry eg. Mouth
Point of exit eg. Salmonella - faeces
TB has the same point of entry and exit

Question 5

What are the direct transmission ?

Answer 5

Direct contact
Droplet infection
Contact with soil
Inoculation into skin or mucosa
Transplacental

Question 6

What is indirect transmission?

Answer 6

Vehicle borne
Vector borne
Air borne
Formites borne 
Unclean hands and fingers

Question 7

Microorganisms can be transmitted via another organism. How is this done?

Answer 7

Vector- mosquito malaria
Intermediate host- tape worm in pigs transmitted to human in uncooked pork
Zoonosis - disease that can infect humans and animals- anthrax, TB

Question 8

List the modes of transmission?

Answer 8

Water- john snow 1849 cholera
Food- TB, botulism, cholera, dysentery, GE
Aerosol droplet,- cold, flu, rubella, TB, strep throat
Vectors- rabies, malaria, sleeping sickness, yellow fever
Direct contact- (contagious(skin) fungal- ringworm) SEX- hep B, STI, Aids

Question 9

What are the risk factors for infection?

Answer 9

Age, immune status, physical well being, mental well being, hygiene, underlying chronic disease, other existing infections, medical interventions, medical therapies

Question 10

What 3 elements are needed for transmission of infective agents?

Answer 10

Source
Susceptible host
Mode of transmission

Question 11

What factors influence disease transmission?

Answer 11

1. Agent- infectivity, pathogenicity, virulence, immunogenicity,antigenic stability, survival
2. Host- age, sex, genotype, behaviour, nutrition status, health status
3. Environment- weather, housing, geography, occupation, air qual., food

Question 12

Give an example of an illness caused by droplet/ aerosol infection?

Answer 12

Bacterial meningitis, cold, influenza, TB, measles, mumps

Question 13

What is cough etiquette?

Answer 13

Influenza, respiratory syncytial virus (RSV), whooping cough, severe acute respiratory syndrome (SARS) spread by cough, sneeze, unclean hands.
Prevent- cover nose and mouth with tissue, dispose, wash hands
Catch it, bin it, kill it.

Question 14

What Is faecal- oral transmission?

Answer 14

Direct contact rare in this route.
Indirect- contaminated food stuff and water
Poor hygiene
Typical mode of infection for cholera, hepA, Polio, rotavirus, salmonella, ascaris lumbricoides

Question 15

What is sexual transmission?

Answer 15

Caught during intercourse.
Tears in genital areas allow entry of body fluid
Responsible for the transmission of- HIV/ aids, chlamydia, HPV, HepB,
Herpes, syphilis

Question 16

What is oral transmission?

Answer 16

Direct- kissing

Indirect- glass, cigarette

Question 17

What is contagious?

Answer 17

A disease that is transmitted by direct contact.
All contagious diseases are infectious but not all infectious diseases are contagious
Contagious diseases often break out in schools eg. Impetigo

Question 18

What is vertical transmission?

Answer 18

Passed from mother to child - in utero or during childbirth

Example HIV HepB, syphilis

Question 19

What is iatrogenic transmission?

Answer 19

Due to medical procedures such as the injection or transplantation of infected material, eg CJD, MRSA

Question 20

What is vector borne transmission ?

Answer 20

Does not cause the disease itself but transmits infection By conveying pathogens from 1 host to another
Example Malaria from mosquito- injects its saliva into secondary host

Question 21

What does obligate mean?

Answer 21

Need host to survive

Must cause disease in order to be transmitted from 1 host to another, eg TB

Question 22

What does opportunistic mean?

Answer 22

Transmit from host to host without the need to cause disease.
Can cause disease if host immune system is compromised, eg, V cholera

Question 23

What does transmission of disease mean?

Answer 23

Passing of a communicable disease from an infected host individual or group to an individual or group
Route of transmission important as patterns vary between populations
Differences in incidence between diff groups throw light on routes of transmission- epidemiology