Infectious diseases can be caused by: Bacteria. These one-cell organisms are responsible for illnesses such as strep throat, urinary tract infections and tuberculosis. Viruses.

Where do infectious agents come from?

Pathogens associated with HAIs are derived primarily from human sources, but contaminated objects and environmental sources are also implicated. Human sources include patients, HCP, house hold members, and visitors.

What causes disease agents?

The agents that cause disease fall into five groups: viruses, bacteria, fungi, protozoa, and helminths (worms). Protozoa and worms are usually grouped together as parasites, and are the subject of the discipline of parasitology, whereas viruses, bacteria, and fungi are the subject of microbiology.