The Centers for Disease Control and Prevention is working with states to investigate more than 1,600 cases. There were 34 deaths confirmed in 24 states as of Oct. 22, the most recent CDC report.
The federal agency says cases of vaping related illness appear to be leveling off, following recent health warnings. Most patients who have come down with the illness reported using products containing THC, the main psychoactive chemical in marijuana.
No specific e-cigarette device or substance has been linked to all of the cases. E-cigarettes are battery-powered devices that heat liquid, turning it into vapor for inhaling. They are an increasingly popular alternative to combustible cigarettes.
Investigators are increasingly focused on thickeners and additives found in illegal THC cartridges sold on the black market. Authorities caution that people who decide to continue vaping should not buy products off the street, and they should not modify or add any substances to the products.
While almost 80% of patients are under 35, older people are far more likely to die from the mysterious lung illness. The average of age of those dying is 49, according to the CDC.
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