1. What are the global patterns of disease and can factors be identified that determine these?

Patterns of disease

Classification

Infectious : A disease spread by parasites, bacteria, viruses and fungi

Non infectious : A non-communicable disease due to age or genetic defects

Communicable : An infectious disease that spreads from host to host

Non- communicable : A disease that cannot be spread between people

Contagious : A disease spread by contact or indirect contact

Non contagious : A disease not spread by contact or indirect contact between people

Epidemic : An outbreak of disease that spreads quickly and affects many people not in a defined geographical area

Pandemic : An epidemic which spreads worldwide Eg. Spanish Flu

Endemic : A disease that exists permanently in a geographical area or human group

HIV

Malaria

CVD

Diabetes

TB

Disease diffusion and spread

Physical barriers to diffusion

Stages of diffusion

Socio-economic barriers to diffusion

Hägerstrand model

Types of diffusion

Hierarchal : Through an ordered sequence of places, large centres to smaller isolated centres Eg. Spanish Flu

Relocation : Disease leaved area of origin and moves into
new areas Eg. Cholera epidemic in Nepal --> Haiti

Expansion : A disease has a source and expands outwards into new areas while the carriers in the source area remain infected Eg TB

Contagious : Spread of disease through direct contact with a carrier. Strongly influenced by distance

Physical factors and prevalence

Zoonotic diseases

Seasonal variations (Monsoons)

Physical factors

Temperature

Relief

Precipitation

Water sources

Ringworm

Natural hazard

Mitigation strategies

Human factors

Impact of disease

Environmental factors

Climate

Sanitation

Water supply

Food

Population density

Access to clean water

Immunisation programmes

National scale

International scale

Infectious but non-contagious tropical disease

Concentrated in Africa, Latin America, South Asia : equatorial regions

Malarial parasite is transmitted to humans by Anopheles mosquitoes which thrive in warm humid environments

Infectious highly contagious disease associated with poverty and overcrowded living conditions

In 2013 there were 9 million cases worldwide and 1.5 million deaths

Africa has the highest number of deaths, with a large proportion among HIV/AIDS sufferers making them more susceptible due to weak immunity

Infectious contagious disease

Spread by human bodily fluids such as blood and semen

Sub-Saharan Africa with South Africa and Nigeria having the largest number of cases

25% of Lesotho and Swaziland carry the disease

In 2015 35 million people infected

Age causes incidence to rise

Russia due to alcoholism (cold climate/ culture)

Sub Saharan Africa and Arabian Peninsula

17 Million deaths a year with 80% occurring in low- and middle income countries

Premature death from lifestyle, tobacco consumption, unhealthy diet and physical inactivity

Non - communicable disease caused by deficiency of insulin, a hormone secreted by the pancreas

Afflicts nearly 250 million people a year and is responsible for 4 million deaths

Type 1 : In childhood as its genetic

Type 2 : In adults and is often linked to obesity, poor diet and physical inactivity

  1. Slow rate of diffusion as few people have it
  1. Infected rate increases rapidly as the disease is passed on
  1. Most people have had the disease so there are less people to diffuse to
  1. Most of the susceptible population have been infected

Deserts

Seas/ oceans

Mountain ranges

Distance

Climate

Political border checks

Imposing curfews to limit contact between people (Covid)

Mass vaccination programmes to protect populations against disease

Cancelling public events

Wearing face-masks in public

The probability of a contagious disease spreading to an area is inversely proportional to distance from its source

Their is a neighbourhood effect in diffusion

The probability of contact between a carrier and a non-carrier is determined by the umber of people living in each 5 X 5 KM grid square and their distance apart

People living in closer proximity to carriers have a greater probability of contracting a disease than those located further away

Creates aquatic habitats such as ponds or stagnant pools which allow disease vectors and insects to flourish

Water borne diseases - Cholera

Flooding can cause the spread of disease

Determines the rates of vector development and behaviour as well as viral replication

Transmission of the flu virus is most efficient at lower temps

Water and wetter conditions favoured the growth and spread of mosquitoes carrying sub-tropical diseases -- > WNV

Altitude causes abrupt changes in climate and disease habitats

In Ethiopia malaria is concentrated in humid lowlands but is largely absent in cooler highlands

High water stress causes people to drink dirty disease filled water

Low water stress : Can afford to move and drink safe water

April - September

Warm moist air from the SW Indian Ocean blows towards India/ Bangladesh. Meeting cold dry air from North ITCZ

Causes a humid climate and torrential rainfall

Linked to malaria as bodies of standing water are created by rain

Climate change

WNV

Climate change

Efforts to limit spread

Reduce exposure

Pesticides and wearing mosquito nets

Reduce risk through organ transplant

Gloves or protective clothing when treating sick animals or when slaughtering

Reducing mosquito transmission

No vaccine available for humans

Vaccines have been developed for horses

Intervention fluids

Hospitalisation

Effects

People over age of 50 or with certain medical conditions are more at risk

Headaches, paralysis, vision loss, convulsions

1/150 severe illness affecting the CNS

1/5 develop a fever, body ache, joint pain

8/10 asymptomatic

Spread through contact with other infected animals, their blood, organ transplant and breast milk (No human - human direct yet )

From bites of infected mosquitoes who get it from infected birds : virus goes into the salivary glands

Zoonotic disease - Infectious contagious

Increased risk of human exposure to WNV

Warmer temperatures accelerate mosquito development, biting rates and the incubation of the disease within a mosquito

Timing of bird migration = long range virus movement

Direct contact with main reservoirs passed on through close contact with infected person, infected animal and object

12,500 new cases annually

Lyme disease

Tick bite with reservoirs in ticks, rodents, deer, sheep and small mammals

Given to humans through the bite of a infected lxodes ricinus tick

Common in Scottish Highlands ( In Bra-ken grass)

2,000-3,00 new cases in England

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