10.1.1—Pathogens and infectious disease

An infectious, or communicable, disease is caused by a pathogen and can be transmitted from an infected host to an uninfected host. A pathogen is the disease-causing infectious agent; the disease is the resulting illness or poor health, not the agent itself.

• Cholera → Vibrio cholerae → bacterium
• Malaria → Plasmodium species → protist
• Tuberculosis (TB) → Mycobacterium tuberculosis and M. bovis → bacteria
• HIV/AIDS → human immunodeficiency virus (HIV) → virus

These named diseases are all infectious because a pathogen is involved and the infection can spread between hosts. The organism type identifies the agent; it does not by itself state how that disease is transmitted or controlled.

Do not call a mosquito the pathogen in malaria: it is a vector, while Plasmodium is the protist pathogen. Do not treat HIV/AIDS as a bacterium, or confuse a pathogen with the disease it causes. Transmission routes belong to 4624; prevention, diagnosis and treatment belong to 4625. No image generated or bound.