Viruses, bacteria, protozoa, and fungi are all examples of what?

Viruses, bacteria, protozoa, and fungi are all classified as pathogens, which are organisms that cause disease in hosts. Pathogens can invade the body, multiply, and lead to various health issues. Understanding that these microorganisms are capable of causing infections and diseases is crucial in the field of esthetics, as practitioners must be aware of potential risks and how to prevent infections during treatments.

In this context, identifying these organisms as pathogens highlights their role in the transmission of diseases, emphasizing the importance of sanitation and hygiene practices in esthetics to protect both clients and practitioners. While "infectious agents" is also a broad term that could encompass all of these, the best choice in terms of the question asked is "pathogens" since it specifically refers to their disease-causing potential. The distinction is important when discussing infection control and safety measures in the esthetics industry.