What is a transmissible disease?
A transmissible (communicable) disease is one caused by a pathogen that can be passed from an infected person to another. A pathogen is a disease-causing organism, such as a bacterium, virus, fungus or protoctist. For example, cholera is caused by a bacterium, influenza by a virus, and malaria by a protoctist. The pathogen may be transmitted directly (through contact or body fluids) or indirectly (through contaminated food, water, air or an animal vector).
Key idea
A pathogen is any organism that causes disease. Transmissible diseases spread from host to host; non-transmissible diseases (such as scurvy) do not.
How pathogens spread
Common routes of transmission include contaminated water (cholera), droplets in the air during coughs and sneezes (influenza), contaminated food, and animal vectors such as mosquitoes that carry the malarial parasite. Understanding the route helps us break the chain of infection.
Controlling the spread of disease
The body has natural barriers — the skin, mucus, hydrochloric acid in the stomach — that reduce the entry of pathogens. We can also reduce transmission through good hygiene: washing hands, safe preparation and storage of food, treating sewage, providing clean drinking water, and controlling vectors. Where available, vaccination protects people before they are exposed.
Remember
- Cholera is a bacterial disease spread by contaminated water.
- The stomach's hydrochloric acid kills many swallowed pathogens.
- Clean water, sanitation and hand-washing break transmission routes.
- A vector, such as a mosquito, carries a pathogen without being harmed.