1a. disease dilemmas - what are the global patters of disease and can factors be identified that determine these?

Infectious disease

Caused by pathogens such as bacteria, viruses, fungi, and parasites. They enter the body, reproduce, and damage tissues or body systems.

Non-infectious diseases

Not caused by pathogens, so they’re not passed on by infection. Examples include rickets, many cancers and deficiency diseases.

Communicable diseases

Can be transmitted from one host to another, either directly between people or indirectly through water, food, surfaces, or vectors. Eg HIV is communicable but not highly contagious

Contagious diseases

Communicable diseases that spread especially easily by close contact, droplets, bodily fluids or contaminated objects. Eg chicken pox

Infectious but not contagious

Because they depend on a vector rather than direct person-to-person transmission. Malaria is the clearest example because it is spread by the Anopheles mosquito.

Non communicable

Can’t be spread from person to person. Include cardiovascular disease, diabetes, and many cancers. Their geography is influenced more by age structure, lifestyle, pollution, income and diet than by infection.

Endemic

A disease is constantly present in a particular place or population at a background level.

Epidemic

Cases rise sharply above the expected level in one region.

Pandemic

The disease spreads across many counties or continents.

Prevalence

Distribution of malaria

• Concentrated in tropical and subtropical regions, especially sub-Saharan Africa

• Found in parts of south east Asia and South America

• Distribution reflects the need for warm temperatures, humidity and breeding water for mosquitoes.

HIV/AIDS distribution

• Global in distribution

• Highest prevalence in sub-Saharan Africa, especially Southern Africa.

• Lesotho, Eswatini, South Africa, and Nigeria stand out due to large populations that have been infected.

Tuberculosis distribution

• Strongly associated with overcrowding, poverty, poor ventilation and weak healthcare access.

• Around 95% of cases are in EDCs and LIDCs, with especially high rates in parts of Africa and Asia.

Diabetes distribution

• Broad global distribution

• Increasingly concentrated in North America, east Asia, and south east Asia.

• Type 1 - biological and autoimmune factors

• Type 2 - closely linked to obesity, diet and inactivity.

Cardio-vascular diseases - distribution

• Coronary heart disease, stroke, hypertension and angina.

• Causes about 17 million deaths per year, and around 80% of these deaths occur in LIDCs and EDC’s because diagnosis and treatment are often weaker.

Overall - disease distribution

Communicable diseases are more common where poverty, poor sanitation, unsafe water and tropical climates dominate whereas non-communicable diseases are more closely linked to ageing populations, urbanisation, affluence, pollution and lifestyle changes.

Hagerstrand model explains…

How disease spreads through space over time rather than appearing everywhere at once. Spread usually starts slow, accelerated quickly, then slows again as barriers appear or the pool of vulnerable people becomes smaller.

The neighbourhoods effect

What does the s-shaped diffusion curve reflect?

Slow, initial spread, rapid acceleration, then levelling off as immunity, treatment, isolation or exhaustion of susceptible hosts slows transmission.

1 - rise, people get it

2 - most people have had it

3 - levels out/decrease

Expansion diffusion

Means disease spreads outwards from its source while remaining strong in the original location.

Eg Spanish flu - killed approximately 50 million people worldwide within a few months.

Expansion diffusion

Means disease spreads outwards from its source while remaining strong in the original location.

Eg Spanish flu - killed approximately 50 million people worldwide within a few months.

Contagious diffusion

• Works through close contact and the neighbourhood effect, so the nearest places are effected first and strongest.

• Influence lessens as you get further away from the origin.

• Eg. 2014-2015 Ebola epidemic in west Africa was spread through direct contact.

Hierarchal diffusion

• Spread throughout groups of people

• Spread around one city and then similar spread occurs in another city.

• HIV/AIDS in USA appeared first in Sam Francisco and then major cities such as LA, NY and then to smaller cities and towns.

Physical barriers

Bodies of water, mountains, distance, climate, remoteness, extreme climates. These can isolate places and interrupt diffusion.

Socio-economic and political barriers

Quarantines, border controls, cancellation of events, mass vaccination programmes, mask use, school closure, treatment capacity and public health messaging.

They can slow disease diffusion but rarely stop it completely when mobility is high.

Factors that hinder reduction in disease diffusion

• Social stigma - eg HIV/AIDS ‘gay disease’ in USA 1970/80s and Russia now.

• Culture/religion - AIDS denial in sun-Saharan Africa, refusal of vaccines due to ingredients.

• Poverty - multiple uses of water sources - sanitation/sewage, showering, washing clothes, cooking, garbage.

• Costs/poverty - lack of access to adequate healthcare, overcrowding, lack of clean water and sanitisation.

• Poor education

• Low status of women (unfair treatment) - education and healthcare.

• Food source eg. Stagnant water in rice paddy fields

• Globalisation - increase in air travel.