What is the essential characteristic of the scientific method

Empirical observation  is the essential characteristic of the scientific method

Explanation:

There are a total of five characteristic of scientific method, among which the Empirical observation is the most important one. Scientific methods depend on right observation of our world and the facts related to it. There is a contrast of this method with subjective methods.

Scientific method should always be empirical, in order to learn all, the factors that are related to the method and to challenge the counter facts. However, the methods vary depending on the various branches of science.

answer:

it could come from a variety of sources.

explanation:

..although it was most likely developed through zoonotic transmission, where an infectious disease which usually afflicts when animals jump to humans.