What characterizes communicable diseases?

Communicable diseases are characterized by their ability to be transmitted from one individual to another, which is why option B is the correct answer. This transmission can occur through various pathways, such as direct contact, air pollutants, contaminated food or water, and vectors like mosquitoes. The defining feature of communicable diseases is this potential for spread, distinguishing them from non-communicable diseases, which cannot be passed between individuals.

The other options provide information that does not encapsulate the essence of communicable diseases. Some communicable diseases can affect a wide range of organisms beyond just animals, including humans and plants. Additionally, while many communicable diseases may have a rapid onset, this is not a universal characteristic, as the speed of onset can vary significantly depending on the disease. Lastly, the causes of communicable diseases include a variety of pathogens, including bacteria, viruses, parasites, and fungi; hence, limiting them to only viruses is incorrect. The ability to spread between individuals remains the fundamental aspect defining communicable diseases.