disease transmittion

• what is a pathogen?

  a microorganism that causes disease
• what is a disease?

  a condition that stops the normal functioning of an organism
• what are the 4 types of pathogen?

  Bacteria, viruses, fungi, protoctista
• what are the 2 ways that pathogens cause disease?

  - damaging host cell/tissues directly

  - producing toxins --> exotoxins are secreted by a living, healthy pathogen
• what is direct transmittion?

  when a disease is transmitted directly from one organism to another
• modes of direct transmittion?

  droplet infection (coughing or sneezing droplets of mucus or saliva directly onto someone)

  sexual intercourse

  touching an infected organism
• examples of diseases spread by direct transmittion

  HIV can be transmitted directly via sexual intercourse

  Athlete's foot can be spread via touch
• what is indirect transmittion?

  when a disease is transmitted from one organism to another via an intermediate e.g. air, food, water, or another organism (vector)
• examples of a disease spread by indirect transmittion:

  potato/tomato late blight is spread when spores are carried between plants - first in the air, then in water

  malaria is spread by vectors: mosquitoes
• what are the 3 factors that affect disease transmittion?

  living conditions, climate and social factors
• How do living conditions affect disease transmission?

  - overcrowded living conditions increase the transmittion of many communicable diseases

  - e.g. TB can be spread indirectly as the bacteria remain in the air for long periods of time and infect new people --> increased risk in crowded living conditions
• examples of how climate affects disease transmittion

  e.g. potato/tomato late blight is common in wet summers as the spores need water to spread

  e.g. malaria is common in tropical countries because hot and humid conditions are ideal for mosquitoes to bread
• social factors:

  e.g. the risk of HIV is high in places with limited access to:

  - good healthcare - people are less likely to be diagnosed and treated for HIV and the most effective anti-HIV drugs are less likely to be available, so it's more likely to be passed on

  - good health education - to inform people about how it's transmitted and how it can be avoided e.g. condoms