The vaping mystery deepens

The clouds around a mysterious vaping illness are stubbornly refusing to part.

The CDC increased its count of cases of the disease in the U.S. to 530 Thursday, while saying they still haven't figured out the cause of the ailment, and that no one product or substance was involved in all cases. "We're leaving no stone unturned," said the FDA's top tobacco official. The agency opened a criminal inquiry into the vaping supply chain. The CDC has opened its emergency center and plans weekly updates.

The message: This disease isn't going away anytime soon.

That the outbreak remains such an enigma is a matter of abiding concern for e-cigarette makers, not to mention worried parents and former smokers who have come to rely on the devices to manage their nicotine habits. The future for vaping looks a whole lot less clear than it did in December, when Marlboro maker Altria plunked down nearly $13 billion for a stake in Juul Labs, maker of by far the most popular vaporizer. Juul, and its backers, and its aspiring competitors, now all find themselves in the crosshairs of election-season Washington.