Disease Dilemmas What explains the patterns in the

Disease Dilemmas What explains the patterns in the spread of diseases?

WHY ARE DISEASES SPREAD? • • • Crowded living + working conditions Inadequate sanitation Unclean water supplies Inadequate nutrition - too little or too much! Low income - no medical help, no resources [e. g. soap/household cleaners, mosquito net/repellent, antiseptic cream etc. Long working hours Physically exhausting work Lack of or inaccessible health care Exposure to health risks at work as legislation is not enforced Inadequate education, e. g. HIV/AIDS sufferers not understanding the concept of safe sex

WHY ARE DISEASES SPREAD? Why might diseases be spreading faster and further than they did in the past? Watch this clip on how pandemics spread.

4 Types of Spatial Diffusion 1. 2. 3. 4. Expansion Contagious Hierarchical Relocation Note: a disease can spread with a combination of above types

1. Expansion Diffusion • Infection spreads out from source in all directions from point of origin. • Expanding disease diffuses outwards into new areas. • The disease often intensifies in the originating area.

2. Contagious Diffusion • Infection is spread through direct contact with the carrier. • Individual hosts carrying the disease pass it on to new contacts. • Strongly influenced by distance - nearby individuals/regions have much higher probability of contact than remote ones. • Contagious spread tends to occur in a centrifugal manner from the source region outward.

Early medical geography map by Jon Snow identifying the cluster + source of a cholera outbreak at Broad Street, London in 1852

3. Hierarchical Diffusion • The infection spreads down through a particular system. • Spreads through an ordered sequence of classes or places, usually form the largest centres with the highest connectivity to smaller, more isolated centres. • E. g. from cities to large urban areas to small urban areas. • Diffusion is also channelled along road, rail and air transport networks which facilitate contact between carriers and a susceptible population.

4. Relocation Diffusion Infection spreads into a new area, leaving behind its origin or source of the disease t 1, t 2, t 3> denote time 1, 2 & 3 respectively

Mixed Diffusion

Which type of diffusion? Spread of HIV in southern Africa along lorry routes Annual number of TB patients per square kilometre in urban Tokyo. In 2009, H 1 N 1 [Swine Flu] Virus - this disease first started in Mexico City, but first saw prevalence in other large cities (LA, NYC, Chicago) before seeing a presence in smaller cities or rural towns. It became a pandemic via international flight routes and airports. In the USA, it resulted in 61 million cases and 12, 500 deaths. Cholera in Haiti 2010 killed 7000 was brought in by emergency aid workers flown in from Nepal. Source: https: //journals. plos. org/plosone/article? id=10. 1371 /journal. pone. 0138831 HIV/AIDS in USA appeared first in San Francisco + then major cities such as LA/ New York - it then spread to smaller cities and then towns

Describe the distribution of child morality rates over 100/1000 in 1851. What might explain this distribution?

What do you think the map on the right is showing?

What explains the same pattern in Child Mortality in 1851 and deaths from Covid-19 in 2020/21?

Read this article – what point is it making? Watch this news clip

Global distribution of deaths from Covid-19 Describe the distribution of deaths from Covid-19 How does this differ from the UK’s national distribution? What might explain the difference?

The role of geography “Geography is necessary to predict the spread and impact of disease. ” Think back over this session and put together an argument in support of the above statement. Draw on examples to support your argument.