Transmission

Question 1

what is direct transmission?

Answer 1

• an individual comes into direct contact with a reservoir of pathogens which are on or in their host

Question 2

what is indirect transmission?

Answer 2

• an individual comes into contact with a pathogen which is outside its host
• these pathogens will have to withstand the harsh environment of being away from their host

Question 3

explain 3 examples of disease transmitted through direct methods

Answer 3

• influenza = droplet infection - small droplets of mucus or saliva that contain the pathogen are expelled from the nose and mouth and land on mucus membrane or are immediately breathed in
• gonorrhoea = sexually transmitted
• hepatitis B = sharing needles

Question 4

explain 3 examples of diseases that are transmitted indirectly

Answer 4

• malaria = spread by bite of a female mosquito = insect is vector
• athletes foot = spread by sharing towels or socks
• cholera = water is vector

Question 5

explain how ‘living conditions such as overcrowding’ is a factor that affects transmission

Answer 5

• droplet infection and airborne transmission spread disease as either fall on to new hosts, or are inhaled sometime later
• poor ventilation makes spread more likely as everyone breathes and re-breathes same infected air
• sharing of beds, towel and utensils increase risk of catching disease, as skin to skin contact more likely

Question 6

explain how ‘social factors such as financial income, education, occupation, and where a person lives’ are factors that affect transmission

Answer 6

• good health care for early diagnosis and treatment of disease reduces spread of pathogen
• education about safe sex practices can provide information to stop the spread of HIV virus
• poorer sewage infrastructure
• both of these things are sometimes only accessible to those who can pay for it

Question 7

explain how ‘climate such as temperature and humidity’ is a factor which affects transmission

Answer 7

• malaria is most common in tropical countries, as mosquitos can’t survive cold winters and therefore can’t colonise in the uk
• also need still water to lay their eggs
• increased heat provided more kinetic energy for chemical reactions so reproduction occurs faster

Question 8

state the 3 ways disease is transmitted directly in animals

Answer 8

• direct contact (touching, sexual contact)
• inoculation (animal bites, needles)
• ingestion (eating, drinking)

Question 9

state the 3 ways disease is transmitted indirectly in animals

Answer 9

• vectors = animals pass pathogen to humans
• droplets = saliva/mucus
• fomites = dirty bedding, cosmetics

Question 10

state how disease is transmitted directly in plants

Answer 10

• direct contact

Question 11

state the 2 ways disease is transmitted indirectly in plants

Answer 11

• contaminated soil = pathogens and spore remain in soil and infect roots
• vectors = wind, water, animals carry pathogens between plants