Pathogens and transmission — Cambridge IGCSE Combined Science

Revision notes

3 short notes, in the order of the specification. Each one in short:

1. Pathogens and how they are transmitted

   A pathogen is a disease-causing organism, and bacteria, viruses, fungi and protists can all be pathogens. A transmissible disease is one in which the pathogen can be passed from one host to another. Transmission can be direct, through blood and other body fluids, or indirect, through contaminated surfaces, food, water, animals or air.

2. Body defences

   The body's defences against pathogens include barriers that keep them out and cells that destroy those that get in. The skin is a tough barrier, nose hairs and mucus trap pathogens, and stomach acid kills most swallowed pathogens. White blood cells destroy pathogens inside the body by ingesting them or by making antibodies.

3. Controlling the spread of disease

   Supplement

   The spread of disease is controlled by breaking transmission routes so fewer people take in pathogens. The main measures are a clean water supply, hygienic food preparation, good personal hygiene, waste disposal and sewage treatment. For example, treating drinking water and sewage stops water-borne diseases such as cholera from spreading.