Physical factors and disease

• Water sources

  Stagnant water affects the prevalence of water-borne diseases;

  parasitic worms in infected water spread diseases.
• Relief

  Altitude leads to falling temperatures and increasing rainfall.

  Flat floodplains can lead to diseases during periods of flood in low-income countries (e.g. dysentery).
• Climate (temperature and precipitation)

  Affects were disease vectors live (e.g. mosquitoes like warm, humid conditions).
• Example of vectors

  Mosquitoes, tsetse files, fleas and parasitic worms.
• Malaria; vector-borne disease affected by physical factors.


  Rainfall (puddles after rainy season)

  Temperature (active between 18 and 40 degrees)

  Humidity (average monthly humidity over 60%)
• Tsetse fly transmits sleeping sickness in west and central Africa, and is lives longer in the wet season due to it being it’s preferred habitat.
• Epidemic of influenza and respiratory illness peak in the winter moths in the Northern Hemisphere.
• Vector-borne diseases transmitted by mosquitoes, flies and ticks peak during the rainy season in the topics and sub-tropics.
• Fly populations are highest in South Asia in pre-monsoon season (March/April) and the end of monsoon season (September/October).
• Freshwater snails (transmitters of bilharzia) follow seasonal lifecycle, following precipitation and temperatures of 10 to 30 degrees.
• Climate change is responsible for Lyme disease and sleeping sickness spreading north.
• Warmer and water conditions mean that malaria will spread terms of their geographical area.
• Sleeping sickness will spread to Southern Africa and affect 77 million people by 2090 due to climate change (WHO).
• Malaria will disappear from East Africa as it becomes too hot due to climate change.
• Spread of zoonotic disease increases where

  Free movement of infected animals

  Prolonged contact between human and animal (e.g. poultry farm)

  Poor hygiene and sanitation

  Unvaccinated animals

  Urbanisation (creating habitats for animals closer to humans)