Infectious diseases
Introduced| English | Meaning |
|---|---|
| infectious disease/ɪnˈfekʃəs dɪˈziːz/ | A disease caused by a pathogen, such as a bacterium, virus, fungus or parasite. |
| pathogen/ˈpæθədʒn/ | Disease-causing agents, such as certain bacteria, viruses, fungi or parasites. |
| transmissible/trænˈsmɪsɪbl/ | transmissible |
| cholera/ˈkɒlərə/ | cholera |
| malaria/mæˈleərɪə/ | malaria |
| vector/ˈvektə/ | An organism or carrier that transfers a pathogen or genetic material to another cell or organism. |
| tuberculosis/ˌtjuːbəkjʊˈləʊsɪs/ | A disease caused by bacteria of the Mycobacterium tuberculosis complex, most often affecting the lungs. |
| immune system/ɪˈmjuːn ˈsɪstəm/ | The cells, tissues and processes that defend an organism against pathogens and other harmful or foreign material. |
The enemy at the gates
- An infectious disease 传染病 is caused by a pathogen 病原体 — an organism that lives in or on a host and causes harm.
- These diseases are transmissible 可传播: the pathogen passes from one person to another.
- You need to know four key examples.
Infectious disease route lab
Classify disease cases by pathogen and route of transmission.
A pathogen is:
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A pathogen causes an infectious (transmissible) disease — e.g. a bacterium, virus or protoctist.
Four diseases to know
| Disease | Pathogen | How it spreads |
|---|---|---|
| cholera 霍乱 | bacterium (Vibrio cholerae) | water/food contaminated with faeces |
| malaria 疟疾 | protoctist (Plasmodium) | bite of an infected mosquito (a vector 媒介) |
| tuberculosis 结核病 (TB) | bacterium (Mycobacterium) | airborne droplets from coughs/sneezes |
| HIV/AIDS | virus (HIV) | unprotected sex, infected blood, mother to baby |
Match each disease to its type of pathogen.
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Pathogens come in several types — bacteria, viruses, protoctists and fungi all cause disease.
An organism that carries a pathogen from one host to another — like the mosquito for malaria — is a ______.
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The mosquito is the vector that transmits the Plasmodium protoctist when it bites.
Cholera is caused by a bacterium and spreads through water or food contaminated with faeces.
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Cholera (Vibrio cholerae) spreads via contaminated water/food — so clean water and sanitation prevent it.
Malaria is caused by a protoctist (Plasmodium) carried by:
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The mosquito is the vector that transmits the Plasmodium protoctist when it bites.
Why HIV is so serious
- HIV infects and destroys certain white blood cells.
- These are the cells that defend the body, so HIV slowly weakens the immune system 免疫系统.
- This leads to AIDS, when the body can no longer fight off infections.
Mycobacterium tuberculosis (red rods) stained in a sputum sample
HIV weakens the body because it:
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HIV destroys certain white blood cells, so the immune system weakens and AIDS can develop.
Pathogens and transmission
- Diseases are caused by bacteria, viruses, fungi and protoctists.
- They spread by direct contact or indirect routes (air, water, food, vectors) — hygiene and clean water break these routes.
Malaria spreads through a mosquito vector: the mosquito carries Plasmodium from person to person
A pathogen is not the same as the disease. The pathogen is the microbe; the disease is the harm it causes. The same pathogen can cause different symptoms in different people.
You've got it
- pathogen = organism that causes disease; infectious diseases are transmissible
- cholera (bacterium, dirty water), malaria (protoctist, mosquito vector)
- TB (bacterium, airborne droplets), HIV/AIDS (virus, sex/blood/mother-to-baby)
- HIV destroys white blood cells → weakens the immune system