Communicable (infectious) disease

Communicable (infectious) diseaseViral diseasesBacterial diseasesFungal and protist diseasesHuman defence systemsVaccinationAntibiotics and painkillersThe discovery and development of drugsMonoclonal antibodiesPlant diseasePlant disease detection

Exam questions worksheet

Pathogens are microorganisms that cause infectious diseases, which can spread from one organism to another. Pathogens include viruses, bacteria, protists, and fungi. They can infect both plants and animals, although most pathogens are species-specific (animal pathogens typically don’t infect plants, and vice versa).

How pathogens cause disease

Once inside the body, bacteria and viruses can reproduce rapidly, allowing infections to spread quickly. Here’s how they cause symptoms:

Bacteria: Some bacteria produce toxins (poisons) that damage tissues, which can make us feel unwell.
Viruses: Viruses invade cells, reproduce inside them, and cause cell damage. This cell damage, along with the body’s immune response, leads to symptoms such as fever, blocked or runny nose, coughing, and sneezing.

How pathogens are spread

Pathogens can be transmitted in several ways:

Direct Contact:
- This includes skin-to-skin contact, sexual contact, shared needles, vectors (such as mosquitoes that carry the malaria parasite), or infected plant tissue coming into contact with healthy plants.
Contaminated Water and Food:
- Pathogens can spread through drinking water, swimming in contaminated water, or eating contaminated food.
Air:
- Pathogens can be carried in tiny droplets or dust particles in the air, which are then inhaled (e.g., when someone sneezes or coughs).

Preventing the spread of disease

We can reduce or prevent infections through several methods:

Good Hygiene:
- Regular hand washing, cleaning surfaces, coughing or sneezing into tissues, and wearing a face mask when ill.
Isolation:
- Keeping infected individuals separate from others, as seen during COVID-19 lockdowns or in isolated areas in hospitals.
Vaccination:
- Immunisations help protect against certain diseases by training the immune system to recognise and fight pathogens.
Destroying Vectors:
- Controlling or eliminating organisms that spread disease, such as mosquitoes (which transmit malaria), aphids (which spread plant diseases), or culling infected animals like badgers that carry bovine tuberculosis.

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