What is the term for substances or organisms that cause disease?

The term for substances or organisms that cause disease is "pathogens." This term encompasses a wide variety of disease-causing entities, including bacteria, viruses, fungi, and parasites. Pathogens are specifically recognized for their ability to invade a host, evade the immune response, and multiply, leading to disease processes.

While the other choices refer to specific types of pathogens—bacteria and viruses are indeed pathogens, and "germs" is often used colloquially to include all pathogens—it is "pathogens" that serves as the umbrella term. It is more precise in a clinical and scientific context, covering all infectious agents, rather than limiting to just one type or group. Understanding this broader classification aids in recognizing the various threats to health posed by diverse microorganisms.