Comprehensive Glossary for NCCID Terms

Infectious diseases are illnesses caused by germs (such as bacteria, viruses and fungi) that spread from person to person, are transmitted by insects or other animals, or are present in the air, water, food, or soil.  A communicable disease is spread from person to person, or from animal to person (e.g., through body fluids or droplets). All communicable diseases are infectious.  But not all infectious diseases are communicable (e.g., tetanus is infectious but not communicable).

The infectious period is when an infected person can spread the disease to others. 

In some specific contexts, the infectious period ends when a person recovers from the disease and not when symptoms disappear.

Infectiousness refers to how easily a disease can be transmitted to others.

Infectious agents are organisms (bacteria, fungi, viruses and parasites) that can produce infection or infectious disease.

A vector is a living organism that carries and can transmit an infectious agent between humans, or from animals to humans.

Health protection involves:

• Ensuring the safety of our environment (water, air, waste, food)
• Preventing the spread of infectious diseases through vaccination, and
• Managing outbreaks and other incidents which threaten public health

The transmission of disease is the way in which infectious agents spread from a source or reservoir to a person.

A reservoir is where an infectious agent lives, grows, and multiplies. Humans, animals, and the environment can all be reservoirs of infectious agents.

Rapid diagnostic testing (also called rapid diagnostic tests, or RDTs) can quickly inform medical staff of results related to certain types of infectious diseases (such as influenza, Covid, STIs, gastrointestinal, or respiratory infections), at or near the point of care. RDTs are also used for travellers returning home. While they represent certain advantages (rapid, inexpensive, and easy to use), these tests are less sensitive than conventional tests, and are not always meant to replace them.

Zoonoses (plural) are infectious diseases that have jumped from animals to humans. Rabies is an example of a zoonosis (singular form).