MADISON, WI (Ben Caxton) — The Centers for Disease Control and Prevention has confirmed at least 450 cases of a severe lung illness linked to vaping nationwide, including Wisconsin. A majority of patients have vaped THC, the chemical in marijuana. But an article in the New England Journal of Medicine finds 17-percent of patients in Wisconsin and Illinois claimed they vaped only nicotine. That baffles Doctor John Meiman, chief medical officer with the Wisconsin Department of Health Services “Our biggest question is what substance or substances could be really responsible for this.” As of late last week, 34 people in Wisconsin have been sickened, with an additional 12 cases needing further investigation. New numbers from the state showing the scope of the problem will be released Thursday.