Transmission of diseases

Taken from IGCSE edexcel human biology student book.

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Droplet infection

  • Many of these are respiratory diseases (diseases that affect the airways of the lungs).
  • The organsisms are carried in tiny droplets through the air when an infected person coughs or sneezes
  • They are inhaled by other people.

Examples of diseases

Common cold, influenze, tuberculosis, pneumonia

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Drinking contaminated water

  • The microorganism transmitted in this way often infect regions of the gut.
  • When a person drinks unclean water containing organisms.
  • They colonise a sutiable area of the gut and reproduce.
  • They are passed out with faeces and find their way back into the water

Examples of disease

Chlorea, typhoid fever, polio

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Eating contaminated food

  • Most food poisoning is bacterial
  • Though some viruses are transmitted in this way
  • The organisms initially infect a region of the gut

Examples of disease

typoid fever, polio, salmoneliosis, listeriosis, botulism

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Direct contact

  • Many skin infections are contracted this way
  • Spread by direct contact with an infected person 
  • Or contact with a surface carrying the organism

Examples of diseases

athlete's foot, ringworm

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Sexual intercourse

  • Organsims infecting the sex organs can be passed from one sexual partner to another during intercourse.
  • Some (such as fungus thrush, which causes candidiasis) are transimitted by direct contact.
  • Others (such as AIDS virus) are trasmitted in semen or vaginal secretions.
  • Some (such as syphilis) can be transmitted in saliva.

Examples of diseases

Chlamydia, syphilis, AIDS, gonorrhoea

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Blood-to-blood contact

  • Many sexually tramsmitted disease can also be transmitted in this way.
  • Drug users sharing an infected needle can transmit AIDS.

Examples of dieseases

AIDS, hepatitus B

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Animal Vectors

  • Many diseases are tramitted by insect bites
  • Mosquitoes spread malaria and tsets flies spread sleeping sickness
  • In both cases, the disease-causing organism is transmitted when the insect bites humans in order to **** blood.
  • Also, flies can carry microorganism from faeces onto food.

Examples of disease 

Malaria, sleeping sickness, typoid fever, salmonellosis

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