Physical Factors

Question 1

Effect of climate (temperature and precipitation) on disease

Answer 1

Climate affects where disease vectors live. The most frequently referred-to example is that of mosquitoes and tsetse flies (which transmit sleeping sickness): both favour warm, humid, tropical conditions

Question 2

Effect of relief on disease

Answer 2

Altitude leads to falling temperatures and increasing rainfall. In parts of Africa, at higher altitudes it is too cold for mosquitoes. Flat floodplains can lead to diseases during periods of flood in low-income countries (e.g. hepatitis A and E and dysentery)

Question 3

Effect of water sources on disease

Answer 3

Stagnant water affects the prevalence of water-borne diseases; parasitic worms in infected water spread diseases

Question 4

Examples of disease vectors

Answer 4

Mosquitoes, tsetse flies, fleas, parasitic worms and some snails

Question 5

Factors affecting malaria (vector-borne)

Answer 5

• Rainfall: puddles at the end of the rainy season
• Temperature: particularly active in places where average temperatures are between 18C and 40C
• Humidity: where average monthly relative humidity is over 60%

Question 6

Examples of vector-borne diseases

Answer 6

Malaria, dengue fever, African sleeping sickness

Question 7

How seasonal variations influence disease outbreaks

Answer 7

• Epidemics of influenza and respiratory illness peak in the winter months in the Northern Hemisphere
• Vector-borne diseases transmitted by mosquitoes, flies and ticks peak during the rainy season in the tropics and sub-tropics
• Fly populations are highest in South Africa in the pre-monsoon and end of monsoon seasons
• Freshwater snails, which transmit bilharzia to humans, follow a seasonal lifestyle pattern linked to precipitation and temperatures of 10-30C

Question 8

Climate change affects on disease

Answer 8

• Warmer and wetter conditions mean that vector-borne diseases will spread more easily
• Climate change is responsible for the northwards spread of Lyme disease and sleeping sickness
• As temperatures increase, the WHO predicts that sleeping sickness will spread to southern Africa, and affect 77 million people by 2090
• Some diseases might disappear as areas become too hot (e.g. East Africa)

Question 9

Conditions for increase zoonotic disease spread

Answer 9

• There is free movement of infected animals
• Urbanisation creates habitats for animals (e.g. foxes) and brings them into close contact with human populations
• There is not an effective vaccination programme for pets and livestock
• Hygiene and sanitation are poor
• There is prolonged close contact between humans and animals (e.g. poultry farms)

Question 10

Examples of zoonotic diseases

Answer 10

Malaria, dengue fever, sleeping sickness, rabies, Asian flu