How are infectious diseases primarily characterized?

Infectious diseases are primarily characterized by their ability to spread between individuals. This means they are caused by pathogens, such as bacteria, viruses, fungi, or parasites, that can be transmitted from one host to another, leading to the potential for outbreaks and epidemics. This transmissibility is what differentiates infectious diseases from non-infectious diseases, which do not spread from person to person and may arise from genetic, environmental, or lifestyle factors.

The capacity for infectious diseases to spread highlights the importance of public health measures, such as vaccination, sanitation, and isolation, in controlling outbreaks. Additionally, understanding how these diseases spread helps researchers develop methods for prevention and treatment.

While the availability of surgical treatment, vaccines, or the occurrence of diseases in non-human animals might influence how we manage these diseases, they do not fundamentally define what makes a disease "infectious." Instead, it is the nature of pathogen transmission that is central to the definition of infectious diseases.