What are 3 necessary requirements for infections to spread?

Three necessary requirements for infections to spread are:

1. Pathogen

A pathogen is a microorganism or infectious agent that causes disease. Pathogens can include bacteria, viruses, fungi, and parasites.

2. Reservoir

A reservoir is a place where pathogens can survive and multiply. Reservoirs can include humans, animals, plants, soil, water, or other environmental sources.

3. Mode of transmission

A mode of transmission is the way in which pathogens are transferred from a reservoir to a susceptible host. Modes of transmission can include contact with infected individuals, contaminated surfaces or objects, or through the air.