There are a lot of rumors and unsubstantiated chatter around the risks of vaping, and the CDC admits it has plenty of questions. It says it's too early to pinpoint a single product or substance common to all cases. It's also unclear what role THC-containing products play in the illness, as many patients report vaping both THC- and nicotine-containing products. In the meantime, the CDC cautions anyone who uses e-cig products to beware of symptoms, like cough, shortness of breath, chest pain, nausea, abdominal pain or fever. And in case you needed a reminder, the CDC says you "should not buy these products off the street."

Earlier this week, Michigan became the first state to ban flavored e-cigarettes, and San Francisco was the first city to ban e-cig sales. No matter how vaping is implicated in this CDC investigation, e-cigs have been tied to an increased risk of cancer and heart disease, and manufacturers have been scrutinized by the Federal Trade Commission, FDA and the House and Senate over concerns that e-cig advertising targets teens. While it's too soon to say what's causing this apparently vaping-related lung illness, the CDC is concerned enough to advise against it.