The outbreak of the mysterious vaping-related illness is continuing “at a brisk pace,” with 1,080 cases and 18 deaths across the country, said Centers for Disease Control and Prevention principal deputy director Anne Schuchat on Thursday. That’s an increase of 275 cases from last week’s report — a combination of new patients getting sick and new reporting of previously-identified patients.

As the cases mount, investigators appear to be getting closer to nailing down one of the main causes of the outbreak of mysterious lung injuries linked with e-cigarettes: vaping products containing THC, the main psychoactive chemical in cannabis.

On Thursday, CDC officials reaffirmed that while they haven’t figured out exactly which chemical or device is making people sick, the majority of the cases in both national and state studies to date appear to involve THC-based vaping products. Many of them are illicit products labeled with brand names such as “Dank Vape.”

According to the latest count, about 78 percent of the patients in cases CDC’s analyzed reported using THC-containing products, with or without nicotine, while 37 percent reported only using THC-containing e-cigarettes.

The new findings are consistent with a published analysis of cases by CDC last week. Out of the 514 national cases the agency analyzed, 77 percent had reported using THC-containing products or both THC and nicotine, while 16 percent reported using only nicotine-containing products. The CDC also shared more details about the groups hardest hit: more than two-thirds are male, with a median age of 23. Sixty-two percent are ages 18 to 34, and more than half are under the age of 25. Ninety-one percent were hospitalized. Among the states with the most cases to date: California, Texas, Wisconsin, and Illinois.

A separate study, also published in the CDC’s Morbidity and Mortality Weekly Report, focused on patients in Illinois and Wisconsin, and it came to a similar conclusion. Of the 86 patients interviewed, 87 percent said they’d used products with THC. The overwhelming majority (96 percent) of the THC products these patients reported using involved pre-packaged, pre-filled cartridges or pods, which they said they did not tinker with.

These products were bought primarily from “informal sources such as friends, family members, illicit dealers, or off the street.” And while there was no brand linked to all the cases, 66 percent of patients reported use of products under the brand name Dank Vapes.

“Dank Vapes appears to be the most prominent in a class of largely counterfeit brands, with common packaging that is easily available online and that is used by distributors to market THC-containing cartridges with no obvious centralized production or distribution,” the report read. Other brands patients most commonly reported using included Moon Rocks, Off White and TKO.

One caveat: The CDC’s investigation is ongoing. It’s also possible that, in the coming weeks, the agency will uncover another chemical, product, or brand linked to the cases. The studies also involved self-reported data, and it’s possible people don’t remember what they used or are reluctant to share the details of their vaping or THC habits. The brand details came from just two states, and the picture may look different in other parts of the country.

But for now, “The outbreak is pointing to a greater concern around THC-containing products,” Schuchat warned. At this time, she added, officials still aren’t narrowing their investigation at all. So the agency continues to advise everybody — except smokers who are vaping to quit combustible cigarettes — to avoid using e-cigarettes. It’s also adding an extra caveat: Be especially wary of THC-containing e-cigarette products.

A new study found the lung damage in this outbreak resembles people exposed to chemical spills

As of October 1, health officials in 48 states and the US Virgin Islands reported 1,080 confirmed and probable lung injury cases associated with e-cigarette use. The 18 deaths, meanwhile, have been recorded in 15 states.

Patients who have come down with the mystery lung injury started to experience symptoms anywhere from a few days to several weeks after using e-cigarettes. So far, the patients have a few things in common, according to the CDC. They suffered from respiratory symptoms, including coughing, shortness of breath, chest pain, and difficulty breathing. Nausea, vomiting, diarrhea, fatigue, abdominal pain, fever, and weight loss were also common symptoms.

On X-rays, patients’ lungs appear to be inflamed, as if a pathogen infected them. A new report, published in the New England Journal of Medicine, looked at biopsies of lung tissues from the people affected by the vaping-related illness. They found damage that resembled exposure to inhaled toxic substances, such as during a chemical spill.

When doctors have tried to find a common bacterial or viral source of the disease, they’ve failed to turn anything up. Again, patients only have vaping in common, but no specific products or substances link all the cases together. That’s why an investigation is still underway, and officials are urging doctors and the public to report cases. People who are concerned they’ve been harmed by an e-cigarette product should also contact their health care provider or local poison control center at 1-800-222-1222.

The outbreak isn’t the first to raise questions about the safety of vaping. From nicotine-induced seizures to injuries from vaping explosions to stress on the lungs and cardiovascular system, doctors and health researchers have been calling attention to vaping’s harms. But it is the first time vaping has been linked directly to deaths.

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