A smoker is engulfed in vapors when he smokes an electronic steam engine.
Tolga Akmen | AFP | Getty Images
A deadly lung disease linked to gunfire has killed more than two dozen people in 21 states as U.S. health officials struggle to identify an exact cause of the outbreak, Centers for Disease Control and Prevention said Thursday.  The number of deaths jumped from 18 last week to 26 with 219 new cases diagnosed in the past week, the CDC said, using data that was tracked until Tuesday. The agency said the total number of probable cases is now 1
The health ombudsman still does not know what makes people sick. Of the cases where doctors know what patients were using, about 76% of them said they armed THC, the active ingredient in marijuana, while 13% said they used nicotine exclusively, according to the CDC.
The disease mostly affects men and 80% of patients are under 35, the CDC said. The median age of patients who have died is 49, from 17 to 75 years old.
Dr. Last week, Anne Schuchat, CDC's chief executive, called the illnesses a "very concerning outbreak" with no signs of reducing.
"We have not seen a measurable drop in the incidence of new cases," she said at the time. "The data we have seen does not indicate that it has reached a peak, it does not indicate that it is declining."
The CDC has sent more than 100 doctors and investigators since the lung disease began to emerge as a public health threat in July. The doctors initially said that the disease was similar to a rare form of pneumonia caused by oil in the lungs, but new research doubts that theory.
Researchers at the Mayo Clinic published a study that said a mixture of "toxic chemical fumes," not oils, may be what makes patients sick. They examined lung biopsies from 17 patients suspected of having the mysterious disease.
E-cigarettes are generally considered less harmful than traditional cigarettes. However, public health officials say the long-term health risks are unknown.
The CDC recommends that consumers stop steam, especially THC and especially everything bought away from the street.
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