Final answer:
A virus that has crossed the animal/human barrier and has infected humans, recently reaching a pandemic level with the H1N1 strain is an example of zoonotic disease transmission.
Step-by-step explanation:
A virus that has crossed the animal/human barrier and has infected humans, recently reaching a pandemic level with the H1N1 strain is an example of zoonotic disease transmission. In this case, the virus H1N1, also known as the Spanish Flu, originated from animal sources and spread to humans, causing a global pandemic. The virus was able to jump from animals to humans, leading to widespread infection and transmission among humans.