The problem is that we exploit the land animals are on. People build suburbs in areas where these diseases are endemic. E.g., they clear cut a forest near caves and build a massive suburb, and people move in for the cheap housing. The bats that lived in the forests and caves are pushed to the eves of houses. Ebola virus is naturally endemic in those bats, and when a bat shits, it lands on a picnic table. Some mom sets up a picnic on the table and brushes off what she thought was a stick before serving sandwiches and touching her itchy face.

She handles wet grapes that are for the entire fourth grade class picnic, and everyone ingests them. The next day, multiple children get sick, but one family flew to Yellowstone that evening, and another flew to Japan for spring break, spreading the disease internationally before humans are even aware such a disease has even started.

Three weeks later, the health authorities see a mysterious disease in local hospitals, but have no tests for it, and the local health authority doesn’t issue a shutdown notice for schools because it’s become politicicized and they will lose their job if they make a bad call. A few people dying will get them a repremand at most. That’s how pandemics start.