Disease Dilemmas SG1
What are the Global Patterns of Disease and can Factors be Identified that Determine
These?
KEY IDEA 1.a.: Diseases can be Classified and their Patterns Mapped. The Spread of Diseases is
Complex and Influenced by a Number of Factors
Classification of Diseases
Diseases can be classified as…
Infectious – a disease caused by a pathogen such as a bacteria, virus, parasite or fungus (e.g.
pneumonia)
Contagious – spread from person to person (e.g. HIV)
Communicable – spreadable host to host (host may be an insect, animal or person), may or may not
be contagious (e.g. malaria)
Non-Communicable – any disease which can’t be spread between people because it is non-infectious
and non-contagious, it is caused by lifestyle (e.g. diabetes)
Zoonotic – infectious diseases transmitted from animals to people (e.g. rabies)
ALL CONTAGIOUS DISEASES ARE INFECTIOUS BUT NOT ALL INFECTIOUS DISEASES ARE CONTAGIOUS E.G.
TETANUS
Diseases can also be classified as…
Endemic – disease which is permanently found within a particular geographical area (e.g. malaria)
Epidemic – large number of people with the same disease within a defined geographical location (e.g.
Ebola)
Pandemic – worldwide spread of an epidemic (e.g. HIV or Black Death)
Patterns of Diseases
1. Malaria
Classification – infectious, communicable, non-contagious
Cause – the Plasmodium Falciparum parasite is spread by the female Anopheles mosquito. If a mosquito bites
a person, the parasite enters the bloodstream and travels to the liver.
If a mosquito bites a person already infected with malaria, it can also become infected and spread the parasite
on to other people. However, malaria can't be spread directly from person to person.
Distribution:
Nearly 50% of the worlds population is at risk of malaria – 95 countries
Occurs mainly along the equator and in the southern hemisphere
Mostly in South America, Central Africa and Asia
Why is it Distributed Like This?
Local Factors Global Factors
High population density, low sanitation Climates of 16 – 32oC
standards, poor healthcare Mosquitoes thrive in warm, humid
Low altitude means higher temp = more environments where there is stagnant
mosquitoes water
At altitudes over 1500m and where rainfall
is below 1000mm malaria transmission
decreases
2. HIV/AIDS
, Classification – infectious, communicable, contagious
Cause – Spreads from person to person through bodily fluids, unprotected sex, sharing contaminated needles
and unsafe blood transfusions
Distribution:
Significantly varies across the globe
High proportion in sub-Saharan Africa
Why is it Distributed Like This?
LIDCs have a lack of knowledge, funding and resources to protect against it
3. Diabetes
Classification – non-infectious, non-communicable, non-contagious
Cause – Lifestyle or genetics
Type 1 – Can’t produce insulin
Type 2 – Smoking, lack of activity, diet
Distribution:
High concentration in developed countries e.g. North America
High in China, Russia, Brazil
Why is it Distributed Like This?
Developed countries have more choice over lifestyle and it is rising in lower to middle income countries as they
have a lack of funding or awareness
4. Tuberculosis
Classification – infectious, communicable, contagious
Cause – A bacterial infection spread by the transmission of mycobacterium tuberculosis from person to person
through the air, due to sneezing and coughing
Distribution:
High distribution in poorer areas – 95% of deaths in low-middle income countries
New cases in sub-Saharan Africa, especially near the equator
High in Southern Africa
Why is it Distributed Like This?
Poor living conditions in poorer communities – high population density, poor ventilation,
overcrowding
Limited access to health services especially in areas affected by civil unrest or war
Higher where immune system is already compromised e.g. due to HIV, malnutrition or diabetes
5. Cardiovascular Disease (CVD)
