Think about it this way without modern technology we have no way to mass produce vaccines. One generation, and thats politely assuming most of us would live, is all it would take to create a formula for a pandemic

Going low/no tech is a formula for billions of people dying. The reason the earths population didnt get this large until the industrial revolution is because too many people died lol. The infrastructure couldnt support that many people.

An estimated 50 million people died from the bubonic plague back in the day. That would never happen now. We have antibiotics that can treat it. Conditions that prevent it. Because of energy. This is why disease is most prevalent in areas of energy poverty.