What is the term for disease-causing agents, such as bacteria and viruses?
vaccines
spores
parasites
pathogens
The body’s first line of defense consists of different types of barriers that keep most pathogens out of the body. Pathogens are disease-causing agents, such as bacteria and viruses. These and other types of pathogens are described in Figure below . Regardless of the type of pathogen, however, the first line of defense is always the same.