Transmission, Importance and Key Definitions for Diseases

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

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)

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

• 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

• 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

• 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

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