IGCSE Biology glossary
Pathogen
Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Definition
A disease-causing organism. For example, bacteria, viruses, fungi or protoctists that cause transmissible diseases.
What to include in an exam answer
One word, one mark, frequently asked. Pair it with 'transmissible disease' (a disease in which the pathogen can be passed from one host to another). The two definitions appear together in Paper 3 and 4.
Example in context
Defining it: 'A pathogen, such as the influenza virus, is a disease-causing organism that can be transmitted from one host to another.'
Related syllabus topic
Diseases & immunity