A biological preparation that provides immunity against a specific disease.

Single-celled microorganisms that can be found almost everywhere, some of which can cause diseases, while others are beneficial to humans and the environment.  They can survive on their own, inside or outside the body.

A very simple microorganism that infects cells and may cause disease. Because they can multiply only inside infected cells, they are not considered to be alive.  They can cause diseases such as the flu, COVID-19.

A medicine that can kill or stop the growth of bacteria, commonly used to treat bacterial infections.

A term used to describe a disease that can be spread from person to person through contact, droplets, or other means.

The body's natural defense mechanism against germs and other foreign substances that can cause disease.

An outbreak of an infectious disease that spreads worldwide or across multiple countries.  COVID-19 is an example of this.