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We are going to be covering a range of diseases, therefore we thought it would be important we have a reference page so you know some of the basics!


  • Microscopic organism

  • Bacteria are single celled organisms with no membrane bound organelles, thus they are called prokaryotes

  • They do not contain a nucleus, instead, their DNA is found in a free floating form known as a nucleoid or a circular piece known as a plasmid. 


  • Microscopic organism (smaller than bacteria)

  • Variety 

  • Viruses contain genetic material in the form of DNA or RNA, protected by a capsid or protein coat

  • Viruses cannot reproduce outside a host cell, they use host cell machinery to replicate


  • Eukaryotic single celled or multi celled organisms

  • They cause disease in plants and animals 

  • They can cause disease when they overgrow and damage tissue


  • Parasites are organisms that live on or in another organism, it gains its nutrients at the expense of its host. 

  • There are three main classes that can cause disease in humans. These are protozoa (single celled organisms), helminths (multi celled organisms), and ectoparasites (multi celled organisms that live outside the body).

Definitions (note that these are in the context of infectious disease)

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Anthropogenic: Term used when relating to humans 

Arbovirus: A name for a virus transmitted by arthropods

Arthropod: An invertebrate, with an exoskeleton e.g. Mosquito, ticks, ants 

Antimicrobial resistance: When bacteria, viruses, fungi and parasites change over time and no longer respond to drugs/ medicines used to treat them 

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Bacteria: Single celled organisms that can live in a diverse range of environments

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Climate Change: A change in climate and weather patterns globally and regionally 

Coronavirus: A large family of viruses

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Disease:  Deviation from the normal structural/ functional condition of an organism, often associated with symptoms

DNA: DNA (deoxyribose nucleic acid) is the molecule that contains an organisms genetic information

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Endemic: When a disease is commonly found amongst people in a give area

Epidemic: The spread of disease across a given population at a specific time 

Eukaryote: Organisms containing multiple cells (Multi-celled). DNA of these eukaryotic cells are membrane-bound. Eukaryote example include; plants, animals, fungi and protists

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Fungi: Multi-celled or single-celled organisms, that can causes disease in plants and animals

Febrile illness: Term used to describe symptoms relating to fever, and sometimes seizure too

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Gene: Segments of DNA that determines the traits of an organism

Genome: The complete genetic material of an organism.

Genus: A biological classification that ranks above species. A genus consists of species with common characteristics. For example Homo is the genus of Homo sapiens

Global Warming: Long term increase in the overall temperature of the earths atmosphere

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Habitat: The natural home/ environment of an organism

Host: The organism in which a bacteria/virus/parasite/fungi is living on or in

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Insecticide: A substance used to kill insects 

Insecticide resistance: A change in the susceptibility of insects to substances used to kill them

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Long lasting insecticidal nets (LLIN): Insecticide treated nets (ITN) used to kill mosquitoes and prevent disease

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Microbe: A microscopic organism

Mosquito-borne disease: Disease transmitted by a mosquito

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Neglected tropical disease: A diverse group of infections, common in tropical regions- which historically do not receive as much attention as other diseases

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Pandemic: The spread of disease across a large area i.e. several continents of globally. For example, Covid-19 

Parasite: An organism that lives in or on another organism, gaining its nutrients at the expense of its host

Pathogen: A disease causing organism. They can be categorised into four groups: bacteria, virus, fungi or parasite

Prokaryote: Single-celled organisms made of a single prokaryotic cell. The DNA in these cells are circular and found free in the cytoplasm. An example of a prokaryote is bacteria

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RNA: RNA (ribonucleic acid) is a complex molecule that is used in the cellular synthesis of protein

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Species: A biological classification that ranks below genus. A species consists of organisms that are able to interbreed and create offspring that are fertile. For example, Homo sapien is the species all humans belong to 

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Transmission: The means by which an infectious agent spreads

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Vector: An organism that transmits pathogens between humans, or from animals to humans

Vector-borne: Disease transmitted by a vector 

Virus: Microscopic organism that can cause illness by using host cell machinery to replicate. An example is HIV. 

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Water-borne disease: Disease caused by water contaminated with pathogens i.e. drinking water contaminated with cholera bacteria

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Zoonotic disease: A disease that can be transmitted between animals and humans

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