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Biological Disease (AQA A Level Geography)

Revision Note

Robin Martin-Jenkins

Written by: Robin Martin-Jenkins

Reviewed by: Bridgette Barrett

Prevalence & Distribution of Malaria

Prevalence, Distribution and Seasonal Incidence of Malaria

  • Malaria is a communicable (infectious) disease found in tropical areas

    • It is biologically spread by disease vectors - parasites carried by female mosquitoes

  • Prevalence means the proportion of a population who have a specific characteristic in a given time period

    • Nearly half of the world’s population is at risk of malaria

      • In 2020, an estimated 241 million people contracted malaria in 85 countries, killing around 627,000 people

    • Infants and children under 5 years of age, pregnant women and patients with HIV/AIDS are most susceptible to dying from severe malaria

    • Migrants, mobile populations and travellers are also vulnerable if they enter areas with intense malaria transmission 

    • Some adults in areas where malaria is common will develop partial immunity which reduces the risk that malaria infection will cause severe disease

  • Distribution refers to the pattern of health events in a population

malaria-1
Distribution of confirmed cases of malaria per 1000 population, 2015

  • Seasonal incidence of malaria depends on physical factors

    • Greatest incidence of the disease occurs during and soon after the season of highest rainfall

    • Due to mosquitoes breeding in stagnant water supplies

    • Malaria can be present throughout the year in equatorial regions where seasonal variations are less marked - known as ‘malaria endemic’ areas

      • E.g. Central African belt of the Congo basin, including parts of Equatorial Guinea, Cameroon, Congo, Democratic Republic of Congo, Rwanda, Uganda and Kenya

Examiner Tips and Tricks

When revising, try and learn some specific countries or regions where malaria is most prevalent. For example, rather than just saying it is found in Africa, be more specific with where in Africa.

Malaria & its Impact

Impact of Environment on Malaria


Links to Environment


Impacts on malaria transmission





Physical

  • Areas of stagnant water, present during rainy seasons, are breeding grounds for mosquitoes

  • Transmission rates fall where annual rainfall is less than 1,000mm

  • Malaria parasites can only survive in temperatures between 16°C-32°C

  • Altitude can affect the ability of mosquitoes to breed, so incidences of malaria are rare in highlands above 1,500m altitude.

  • Areas near coasts and forests tend to have higher humidity with less seasonal temperature variation, so are more likely to be breeding grounds for transmission vectors












Socio-economic

  • Poverty is a malaria risk factor due to lack of investment in prevention programmes such as mosquito nets

  • Strong correlation between poor quality of housing and increased rates of disease, as ill-fitting doors and open windows allow mosquitoes enter houses freely

  • Areas of high population and housing density allow fast transmission of disease vectors

  • Poor diet and unstable food supply leads to malnourishment, particularly in children, and reduced ability to fight infection

  • Better education systems and higher levels of literacy lead to more knowledge about malaria prevention

  • Strong link between poor sanitation and malaria - open sewers attract mosquitoes

  • Employment type can affect a person’s exposure to malaria. The following all increase the risk of contracting the disease:

    • Agricultural workers living and working near irrigation channels

    • Migrant workers who move seasonally from highland areas to lowland coastal areas

    • Workers in open mines near water sources

  • Age is a risk factor - children under five and the elderly most at risk as less able to fight the infection

Impact of Malaria on Health and Well-Being

  • Malaria affects people’s quality of life and their physical, mental and economic well-being

impact-of-malaria-1
Impact of malaria on health and well-being

Examiner Tips and Tricks

A 9 or 20 mark question is likely to ask you about more than one section of the topic. Make sure you are able to assess why malaria occurs in certain places and also how it impacts on people’s way of life. You would be expected in these questions to come to a view as to which causes and impacts are most severe, which might depend on which examples you use.

Management & Mitigation of Malaria

  • Management and mitigation strategies include:

    • Giving antimalarial drugs and vaccines to those living or travelling to areas of transmission

    • Seasonal malaria chemoprevention (SMC) - a programme that delivers antimalarial medicine to vulnerable populations during peak malaria transmission season whether or not the recipient is infected with malaria

    • Treating sick people quickly by making diagnosis tests quicker, more accurate and more widely available

    • Vector controls

      • Insecticide-treated mosquito nets (ITNs) given to vulnerable communities

      • Indoor residual spraying (IRS) - the spraying of insecticide on surfaces within homes to repel mosquitoes

  • These strategies have helped reduce malaria transmission significantly

    • In 2000, 6 countries in malaria transmission zones had fewer than 100 cases. By 2020 that had increased to 26 countries

  • But IRS and antimalarial drugs are expensive and less available to populations in remote rural areas, where they are often most needed

  • Insecticides can have negative knock on effects:

    • People’s health - some have been linked to cancer and miscarriages in pregnant women

    • Death of insects and fish in local water ecosystems

  • There is evidence from Vietnam, Cambodia and Thailand that mosquitoes are developing resistance to insecticides so that they are becoming less effective

    • Research is needed to develop new varieties to outpace the resistance

Examiner Tips and Tricks

Look out for questions that ask you to assess the management strategies of the diseases you have studied. You should try and explain how successful any of the strategies have been as well as pointing out any limitations. For example, the drugs used to treat malaria are effective but can be expensive and so not all people in poorer parts of the world will be able to afford them without help from governments or NGOs.

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    Author
    Reviewer
    Robin Martin-Jenkins

    Author: Robin Martin-Jenkins

    Expertise: Geography Content Creator

    Robin has taught Geography at a number of UK secondary schools over the past 13 years, alongside various pastoral roles. He fell in love with Geography whilst at school and has been a passionate advocate of its importance and relevance ever since. He currently works in an independent secondary school where his teaching is combined with mentoring of younger teachers.

    Bridgette Barrett

    Author: Bridgette Barrett

    Expertise: Geography Lead

    After graduating with a degree in Geography, Bridgette completed a PGCE over 25 years ago. She later gained an MA Learning, Technology and Education from the University of Nottingham focussing on online learning. At a time when the study of geography has never been more important, Bridgette is passionate about creating content which supports students in achieving their potential in geography and builds their confidence.