COVID-19 Glossary

This glossary is intended for journalists, content creators, and health communicators to use to report on the COVID-19 pandemic and related issues. The information is based on rigorous science and is a useful tool for countering misinformation. The glossary terms can be accessed alphabetically, by category or cross-reference, or by search.

Click on the term to get a longer definition and cross-references.

Acknowledgements: Sources consulted for the glossary include the World Health Organisation, GAVI – The Alliance, the US Centers for Disease Control (CDC), Africa CDC, London School for Hygiene and Tropical Medicine, Johns Hopkins University, US National Center for Biotechnology Information, Mayo Clinic, the US Food and Drug Administration,, and The Conversation.

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An acute inflammatory reaction in the lungs, caused by many disorders, and resulting in lung failure.
An ingredient or substance (e.g. aluminium salt) that is added to some vaccines to boost the body’s immune response to that vaccine.
Otherwise referred to simply as an ‘adverse event’, this is an unexpected medical problem that could happen in volunteers in trials of a candidate vaccine or after the rollout of a vaccine. 
A particle measuring 5 microns or less and is light enough to float for hours in the air. They are mainly involved in airborne transmission of a virus and even minimal movements of air such as a small breeze can help carry away the aerosols containing viruses.  Aerosols can transmit infection across distances. 
Also called a travel corridor, it allows tourists to travel between two countries without restrictions such as a mandatory quarantine at either end.  
The spread of a virus from an infected person to an uninfected person, who is exposed to small virus-carrying droplets and aerosols that are suspended in the air over long distances (usually more than six feet/1.8 meters) and over time. When the exposed individual breathes in the virus-carrying air particles, they can become infected.
Tiny air sacs at the end of the bronchioles (tiny branchlike air tubes) in the lungs. They are essential for the process of oxygenating blood and get rid of carbon dioxide (CO2) from the body.
Individuals or systems that provide the necessary conditions for pathogens to multiply rapidly and to become major sources of transmission of viruses or bacteria to the wider community.
When a person partially or completely loses their sense of smell.  
A Y-shaped protein found in the blood and produced by the B-cells of the body’s immune system in response to an invading foreign substance or antigen. Antibodies protect the body from disease by binding to these invaders and destroying them.