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Global patterns of HIV:

Situation and trends - Explain the global distribution of HIV

Number of people (all ages) living with HIV

As of 2012, the global number of people living with HIV is 35.3 million [32.2 million–38.8 million], 

compared to 30.3 million [27.2 million–33.1 million] in 2001 – a 17% increase. This reflects the 

high numbers of people newly infected with HIV along with significantly expanded access to 

antiretroviral therapy, which has helped to reduce the number of people dying from AIDS-related 

causes, especially since 2004–2005.

Sub-Saharan Africa still bears an inordinate share of the global HIV burden. Although the rate of 

new HIV infections has decreased, the total number of people living with HIV continues to rise. In 

2012, that number reached 25.0 million [23.5 million–26.6 million], 71% of the global total.

Source: http://www.who.int/gho/hiv/epidemic_status/cases_all_text/en/

March 20th 2014 15:01

The spread of Disease - Disease Diffusion:

Explain how the geographic concepts of diffusion by relocation and by expansion 

apply to the spread of diseases. 

Disease diffusion refers to the spread of disease from its source into new areas. 

It is well documented that the incidence of disease is likely to be affected by 

distance so that places closer to the source of a disease are most likely to see 

higher incidence. This can be seen in the graph to the right which shows the 

incidence of AIDs rates falling the further away from its source in San Francisco. 

However, in a globalised world, increasingly connected by an integrated 

transport communication system there is also strong evidence to suggest that 

disease can spread quickly via roads at the national scale and airports at 

regional and global scale.

Disease Diffusion:

Two common types of disease diffusion have been classified as expansion and 

relocation diffusion. 

Expansion Diffusion:

Occurs when a disease spreads from one place to another. In this expansion 

process, the   disease often intensifies, in the originating region. As the disease 

expands into new areas it is likely to weaken. This type of diffusion was 

recognised in the recent H1N1 flu virus that had its source in Mexico.

Relocation diffusion: 

Spatial spread process, whereby the disease leaves the areas in which it 

originated as it moves into new areas. An example of relocation of disease can 

be seen in the migration of disease carriers, whether it be a migrant with HIV or 

measles. The spread of cholera in Haiti in 2010, which killed 6000 people was 

thought to be brought into the country by aid workers from Nepal in the 

emergency response to the earthquake. It is quite common to see a mixture of 

two or more types of disease diffusion. The diagram to the left shows a mix 

between expansion and relocation. 

Barriers to the Spread of Diseases:

Barriers of disease diffusion can be classified in terms of natural physical barriers and human 

measures.

Natural Physical Barrier:

The most important natural barrier is that of distance decay. The further a place is away from 

the source of incidence the lower the incidence of disease. Other natural barriers relate to 

remoteness. Remote regions such as rural peripheries, mountainous regions and regions of 

extreme climate experience relatively small amounts of in and out-migration. As a result the 

spread of disease into these regions is less likely. Mountains and oceans also act as major 

natural barriers to the spread of disease as they contain people and restrict migration. 

Human Barriers:

Human measures relate to socio-political structures such as political borders and migration 

control, which restrict or prevent the movement of people. US migration policy specifically 

prevents the immigration of foreigners who carry infectious diseases. At times of high risk 

borders can be completely closed, however for the economic impacts of such a measure it 

would need to be an extreme case. Other human controls relate to the management of 

disease and directly to the way in which a disease is transmitted. In the case of the H1N1 flu 

virus many measures were adapted in the UK. Initially, people who contracted the flu were 

isolated in their homes. This later became a bit of a farce as these same people were giving 

media interviews from their house windows. 

Isolation is of course an important management measure for many diseases though, and is essential for 

highly infectious diseases such as cholera. Other measures in the UK involved creating a heightened 

awareness of improved hygiene. People were advised to refrain from typical greeting customs such kisses 

and hand shakes and to wash their hands carefully. In public places like airports and railway stations 

people wore face masks. In Catholic ceremonies people refrained from drinking directly from the challice 

during the celebration of the Eucharist. Finally, authorities considered cancelling larger public events such 

as sports events and pop concerts. These events at the time all saw reduced attendance. 

Describe the factors that have enabled reduction in incidence of a disease.

http://thebritishgeographer.weebly.com/the-spread-of-disease-and-its-

management.html

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