Viruses were jumping across species over 4000 years ago. Smallpox likely started as a camel virus in North Africa.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4379562/


Yellow fever was a primate virus in Africa 3000 years ago... and still is.

Dengue originated in monkeys about 800 years ago.

Measles started out as a Cattle disease, diverging from rinderpest between the 11th and 12th century.

https://www.ncbi.nlm.nih.gov/pmc/art...413928208title


The ancestral Varicella-Zoster Virus (VZV), that causes chicken pox and shingles, co-evolved with apes, hominids and humans. Along with VZV, its closest alphaherpesvirus relatives herpes simplex 1 (HSV1, ‘cold sores’) and herpes simplex 2 (HSV2, genital herpes) have a common ancestor that is approximately 120 million years old. If the age estimates for the herpes phylogenetic tree are accurate, the evolution of the alphaherpesviruses (VZV, HSV1, HSV2) coincides with the split of Africa from the supercontinent Godwanaland.

Viruses jumping species has been going on for a LONG time. Modern things like - well, airliners, might facilitate the spread somewhat, but it doesn’t cause it. And we’ve been omnivores since before Neanderthal days, so I don’t think you are going to get the world to suddenly go vegan.