1.b. Relationship between physical factors and disease prevalence

How does temperature affect the pattern of diseases?

• Warmer temperature could influence the rate of vector development and replication

Name some diseases which are endemic to lower-income countries with warmer temperatures?

• Malaria

• Dengue Fever

• Yellow Fever

How does precipitation affect the pattern of diseases?

• Rain and humidity creates breeding grounds for disease vectors (stagnant pools)

How does relief affect the pattern of diseases?

• Relief (the height and shape of the land’s surface) affects the altitude of the land, altering the climate and disease habitats

Name an example of how relief affects the pattern of disease?

• Ethiopia - malaria is concentrated in the warmer, humid lowlands but it is less frequent in the cooler, dry highlands

How does water sources affect the spread of disease?

• In deprived countries, millions of people rely on water from unsanitary sources such as wells or sewage-contaminated areas

Name an example of how water sources affects the pattern of disease?

• West Africa - copepod vectors replicate in water sources which spreads the parasite Guinea worm

What are physical factors?

• Temperature, weather and urbanisation

What are disease vectors?

• A living organism that carries and transmits an infectious pathogen

Name an example of physical factors can influence vectors of disease?

• Dengue fever in the tropics - climate (32-34c°) controls the dengue fever epidemiology and the life cycle for the Aede mosquito

What is seasonal bias?

• A data sample containing disproportionately more data from 1 season

How does seasonal variations affect the spread of influenza and the flu?

• Temperate regions in the northern hemisphere - epidemics of influenza peak during the winter, increased rate of transmission at lower temperatures (<5°c)

How does seasonal variations affect the spread of vector-borne diseases?

• Tropics/Subtropic regions - epidemics of vector-borne diseases peak during the rainy season

Name an example of a vector-borne disease which is affected by droughts?

• Bilharzia - trematode flatworm hosted by freshwater snails

Name an example of a vector-borne disease which is affected by monsoon rains?

• Diarrheal disease

What does climate change do to the environment?

• Increases global temperature, rainfall and humidity

• Stimulated the transmission of vector-borne diseases and extended their geographic range

How does the impact vary for climate change?

• Geographical location

• Socio-economic status

What conditions does climate change provide?

• Warmer and wetter conditions which has increased the prevalence of vector-borne infectious diseases

How is the West Nile Virus affected by climate change?

• Culex mosquito, with birds as the host

• Global disease, but prevalent in regions with higher temperatures (Africa, N/S America, Australia)

How is African trypanosomiasis affected by climate change?

• Tsetse fly

• Endemic in 36 Sub-Saharan countries (20.7-26.1°c)

• As global temperatures rise, the disease is likely to spread to Southern Africa (the larvae may die from the heat)

How are tick seasons affected by climate change?

• Lyme disease

• Thrives in hot and humid climates (some mild winters allow ticks to survive and stay active for a longer time)

• Lyme disease is likely to spread northwards to Canada from the USA

What are zoonotic diseases?

• Infectious diseases that are spread from animals to humans (domestic and wild)

Which conditions do zoonotic diseases need to spread?

• The movement of infected wild animals are unrestricted by physical barriers

• Vaccination of pets and domestic livestock is sparse

• Limited control within urban areas of feral animals

• Poor hygiene and sanitation

How does bird flu spread?

• Influenza A viruses

• Contact with secretions or droppings

• Respiratory issues

• Preventable through hygiene and sanitation

How does rabies spread?

• Lyssavirus genus

• Bites or scratches

• Affects the nervous system

• Preventable through vaccination of pets and post-exposure treatment