transmition and definitions

• 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 or 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 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 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
• living conditions:

  • 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
• climate:

  • 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
• what is a parasite?

  An organism that lives or feeds in or on a host, causing it harm