Infectious disease is defined as

Infectious disease is defined as

• A. Caused by harmful organisms or viruses
• B. A disease spread through water
• C. A plant-like organism
• D. A storm drain system

Answer: (A)

Infectious disease means illnesses caused by living germs—such as bacteria, viruses, fungi, or parasites—that can invade the body and multiply. Because these agents can spread between people or animals, the illness is considered infectious. The statement that infectious disease is caused by harmful organisms or viruses best captures this idea, since it includes the different types of pathogens that can cause illness. The other ideas don’t fit: spreading through water is only one possible route, not the definition; a plant-like organism isn’t the standard description of infectious diseases in people; and a storm drain system is unrelated.

Infectious disease means illnesses caused by living germs—such as bacteria, viruses, fungi, or parasites—that can invade the body and multiply. Because these agents can spread between people or animals, the illness is considered infectious. The statement that infectious disease is caused by harmful organisms or viruses best captures this idea, since it includes the different types of pathogens that can cause illness. The other ideas don’t fit: spreading through water is only one possible route, not the definition; a plant-like organism isn’t the standard description of infectious diseases in people; and a storm drain system is unrelated.