Why is a health crisis also an environmental crisis?

COVID-19 is responsible for a seemingly unprecedented world health crisis, but in fact, it has precedents: SARS, AIDS, Mad Cow disease, avian flu, rabies, Ebola, Chikungunya… Are these emerging or re-emerging diseases inevitable, with the only possible response being self-quarantine? Or do they point to our increasingly questionable relationship with the natural world around us?
Revised 3rd edition.