Answer & explanation:
Most living things carry a variety of pathogens, such as bacteria and viruses. The evolutionary survival of these pathogens depends exclusively on the infection of new hosts.
The main factor for combating a pathogen is the host's immune system, so the immune status of the new host is also the main factor for the pathogen to jump into it.
Environmental factors can also influence the ease of infection of a pathogen, such as the change in human behavior and localization over the years.
In addition, the growth of cities brings them closer and closer to wildlife, and these wild animals end up feeding on residues left by humans and this can directly influence the transmission of pathogens.
The presence of a particular vector can also influence the ease of a pathogen to jump from one individual to others if not combated correctly, such as mosquitoes, beetles, snails and others.