Emerging infectious disease is defined as:

$$ Any disease$-$causing infectious agent spread by direct or indirect contact

A type of illness caused by a pathogenic agent, including viruses, bacteria, fungi, protozoa, parasites, or abnormal proteins $($prions$)$

The process by which regional economies, societies, and cultures are becoming integrated through a global network of trade, migration, communication, and the spread of new technology

The process of the introduction of pathogens, their transmission and adaptation into human populations, which results from a complex interaction of host, agent, and environment