Transmission, Importance and Key Definitions for Diseases

  • Created by: Tilly
  • Created on: 21-01-13 17:14


HOW MALARIA IS TRANSMITTED (Plasmodium falciparum)

  • Female Anopheles mosquito bites host and draws blood
  • if host has malaria, parasitic gametes are sucked into its stomach
  • gametes fuse and form zygotes which develop in mosquito's stomach
  • they become infective stages and move to the mosquito's salivary glands
  • when mosquito bites, it injects some saliva to act as an anticoagulant, which contains the infective stages of the parasite
  • in the human host the infective stages enter the liver, where they multiply
  • move out into the bloodstream again and enter red blood cells where the gametes are produced
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TRANSMISSION OF HIV/AIDS (human immunodeficiency virus)

- Can be transmitted in following ways:

  • exchange of body fluids such as blood-to-blood contact
  • unprotected sexual intercourse
  • blood transfusions that have not been screened
  • unsterilised surgical equipment
  • sharing hypodermic needles
  • across placenta or during childbirth
  • from mother to baby during breast feeding
  • accidents such as needle stick (pricked by a sharp object)
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TRANSMISSION OF TUBERCULOSIS  (mycobacterium bovis/tuberculosis)

  • TB is spread in the droplets  of liquid released by the sneezing, coughing and talking of an infected person.
  • in particularly undeveloped countries TB can be spread by milk and meat of cattle.
  • Factors which can aid the spread of TB:
  • overcrowding (lots of people living in one place)
  • poor ventilation
  • poor health (one is more likely to contact TB if one has an illness already, particularly HIV/AIDS)
  • poor diet
  • homelessness
  • living/working in or with people from areas where TB is common
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Importance of Malaria

  • kills 3 million people every year
  • 300 million people affected worldwide every eyar
  • limited to areas where Anopheles mosquitoes can live (tropical regions)
  • 90% of those with malaria live in sub-Saharan Africa
  • global warming may increase the area in which the Anopheles mosquito can live
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Importance of HIV/AIDS

  • world wide disease
  • spreading like a pandemic
  • in 2005 there were 45 million living with HIV/AIDS; more than half were in sub-Saharan Africa
  • 5 million people newly infected every year
  • nearly 30million people at end of 2005 had died from HIV/AIDS related diseases
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Importance of TB

  • worldwide disease
  • 1% of world's population is newly infected every year
  • 10-15% of those people then go on to develop the disease
  • 2005: - 8.8million people new cases recorded   -1.6million people died
  • Particularly common in SE Asia and sub-Saharan Africa, rising in Eastern Europe
  • New strains of Mycobacterium that are becoming resistant to available treatments
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Key Terms for Disease

Prevalence: the number of people with a disease at any one point in time

Incidence: number of new cases in a population per year

Mortality: the number of people who die from a disease per year

Morbidity: the number of people with the disease as a proportion of the population

A disease can be...

an Endemic: always present in the population

an Epidemic: spreading rapidly to a large number of people over a large area

a Pandemic: a worldwide epidemic

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