Wow, after reading this, I guess I never knew much about the human body, haha. The climate change point is very concerning. There's even evidence that climate change may have contributed to the emergence of COVID-19 through its impact in shifting bat populations. Here's a source if you're interested. :))

https://medium.com/microbial-instincts/the-defining-factor-in-coronavirus-outbreaks-may-have-been-climate-change-5e553533f9f9