genreal Flashcards
diffusion
disease is spread outwards from the orgin and across in a process called diffusion, the diffusion concept applies to inovations, migration and settelment as well as the spread of the disease
diffrent types of diffusion
-expansion
-relocation
-contagious
-hierachel
expansion diffusion?
in expansion diffusion a disease has a source and spreads outwards into a new areas. meanwhile the carriers of the disease in the source area remain infected
example of expansion diffusion?
TB
relocation diffusion?
occurs when a disease leaves the area or origin and moves into a new area .
example of relocation diffusion?
cholera epidemic in haiti 2010, the diease which orignated in nepal brough to haiti by international aid workers that had flown in to help with the disaster
contagious diffusion?
describes the spread of disease through direct contact with the carrier, it is strongly influenced by distance
example of contagious diffusion?
ebola epidemic in west Africa that started in 2014 is a classic example of contagious diffusion
the covid 19 pandemic is another example and due to globalisation the diease became widespread rapidly
hierarchal diffusion
a disease spreads through an orders sequence of places usually from the centers with the highest connectivity to smaller more isolated centers
transports effect on diffusion?
diffusion is also channels along road, rail and air transport networks which facilities contact between carriers and a subseptiable population
in 2009 the H1N1 flu virus became a pandemic via internationl flight routes and airports. in the USA it resulted in 61million cases and 12,500 deaths
hagerstrands diffusion model?
hagerstrads origianal diffusion model was developed to sitmulate the spread of farm subsdies however later the model was applied to the contagious disease diffusion
important concepts?
neighbourhood effect - probibiloity of contact between carrier and non carrier detarmined by how many people living in 5x5km square grid
-number of people infected by a epidemic aproximates a s shape or logistic curve over time, after a slow beggining the number accelrates rapidly untill eventaully leveling out
physical barriers to diffusion?
-distance
-climate
-sea and mountines ect
-political bourders
how does climate effect diffusion?
temp, rainfall, humidity vectors are able to thrive and reprdouce more rapidly
seasonal variations
transmittion of the flu viris is more efficient at a lower temperature and when atmospheric humidity is low
due to the vitamin D deficiency this leads people to be more subseptiable to the virus (NORTHEN HEMISPHERE)
how has climate change effected disease?
incraese temp, rainfall and humidity has stimulated the transmittion of vactor bourn disease
climate change is also responsible for the spread of lyme disease, ticks which transmit lyme disease thrive in walmer condense
