I know I mentioned this before but it bares repeating. My wife got deathly I’ll when we live in the city. It was a virus of some sort that made breathing difficult, hell almost impossible at times. It lasted 3 months. She swore she got it riding MUNI. When she got better she dumped MUNI and bought a scooter. It was fun living in the city while we did but I have never been as sick as I was when I lived there.