The coronavirus that has exploded into a pandemic has almost certainly been circulating for several months longer than public health experts first suspected, masked by asymptomatic cases or illnesses incorrectly diagnosed.
https://healthcare.utah.edu/healthfeed/postings/2019/07/vaping-pneumonia.php
https://www.statnews.com/2019/09/06/vaping-cases-rising-dont-know-cause/
https://www.webmd.com/lung/news/20200304/necrotizing-pneumonia-may-be-new-vaping-hazard