1b- physical factors affecting prevalence of disease

Question 1

how does seasonal variations influence outbreaks + an example

Answer 1

the northern hemisphere has flu epidemics in winter when transmission of flu is most efficient at low temperatures (5C) and when humidity is low.
In the tropics, vector-borne diseases are spread by mosquitoes, fleas and ticks, etc., peak during rainy seasons. e.g Diarrhoeal disease in South Asia surges at the start and end of the monsoon season when fly populations are highest

Question 2

how does climate change influence disease distribution

Answer 2

The increased temperature, rain and humidity stimulate the transmission of vector-borne diseases and has expanded where they can go like the spread of mosquitoes carrying the west Nile virus, malaria and dengue fever.
WNV started in Uganda and is now found in the EU, US and Asia due to increased temperature.
Ticks thrive in warm conditions so in the US Lyme’s disease is spreading to Canada.

Question 3

what increases the risk of zoonotic diseases spreading to humans

Answer 3

movement of animals is unrestricted by barriers like mountains

control of diseased domestic animals is unrestricted within a country

when there is prolonged exposure between animals and humans e.g poultry farms and avian flu

Question 4

how do the global patterns of precipitation effect disease distribution

Answer 4

creates aquatic habitats which allow insects and vectors to flourish and breed.
Diarrhoeal disease in South Asia surges at the start and end of the monsoon season when fly populations are highest

Question 5

how do the global patterns of relief effect disease distribution

Answer 5

altitude causes changes in climate and habitats e.g in Ethiopia malaria is high in the lowlands but at higher altitudes where it’s cooler malaria is mainly absent.

Question 6

how global patterns of water sources affect patterns of disease distribution

Answer 6

the developing world relies on sources of water that have been contaminated by sewage and so often have cholera bacteria in them.
Stagnant water sources are habitats for disease vectors like copepod vectors which transmit Guinea worm in west Africa