In this April 11, 2018, file photo, a high school student uses a vaping device near a school campus.AP Photo | Steven SenneThe furor over vaping reached a crescendo this week with two congressional hearings, hundreds of new cases of a mysterious lung disease, upheaval at e-cigarette maker Juul and canceled merger plans between Big Tobacco companies Altria and Philip Morris International.The Centers for Disease Control and Prevention has dispatched more than 100 doctors and investigators to try to figure out what’s making 805 people sick and killed at least 13. The early symptoms include coughing, shortness of breath or chest pain, nausea, vomiting, diarrhea, fatigue or abdominal pain.The Federal Drug Administration and Drug Enforcement Administration have opened a criminal probe into the vaping illnesses while Congress and other agencies conduct their own probes into the e-cigarette industry and market leader Juul.Here’s what you need to know:Outbreak spreadsThe vaping illness outbreak has now spread to 46 states and one territory with public health officials in 10 states reporting deaths.The first illnesses cropped up in April and rapidly increased beginning in July. The first death was reported on Aug 23 in Illinois. The most recent fatalities were reported by health officials in North Carolina and Oregon on Thursday. The disease is mostly hitting men, and all reported cases have a history of e-cigarette or vaping use. Of the cases the CDC has demographic data on, 61.9% of the victims were between 18 to 34 years old and 16.2% are under age 18, the agency said Friday.The specific chemical causing people to fall ill is still unknown. Among the 514 cases where the CDC has data on which substance they were vaping, 76.9% said they used THC and 56.8% reported using nicotine. More than a third of the patients, 36%, said they exclusively used THC while 16% said they only vaped nicotine.It’s unclear what role e-cigarettes have played in the illnesses. Mitch Zeller, director of the Food and Drug Administration’s Center for Tobacco Products, said there’s “no common thread” in hundreds of cases. Most patients said they vaped THC, the marijuana compound that produces a high. But the CDC has not ruled out anything yet, noting that some people reported using only nicotine.Until they have more information, the CDC is urging consumers not to buy e-cigarette products off the street or add any substances that are not intended by the manufacturer. Adults who used e-cigarettes containing nicotine to quit cigarette smoking should not return to smoking cigarettes, the agency said.A ban on flavored e-cigarettesAnne Schuchat, director of the Centers for Disease Control (CDC), testifies during a House Energy and Commerce hearing in Washington, D.C., on Wednesday, Sept. 25, 2019.Alex Edelman | Bloomberg | Getty ImagesAdvertisements of e-cigarettes with young models, bright colors and fruity flavors have been criticized by health officials, lawmakers and parents for attracting young people to vaping. States, local and international health regulators are taking action.Michigan is the first state to ban sales of flavored e-cigarettes, while San Francisco became the first U.S. city to prohibit the sales of flavored e-cigarette products. Boulder, Colorado, has passed a similar measure. Washington state Gov. Jay Inslee directed officials to ban the products on Friday. Israel’s Ministry of Health is imposing an immediate ban on the sales of oil-based flavored vaping pods, according to the Times of Israel. Health and Human Services Secretary Alex Azar said earlier this month that President Donald Trump was preparing a ban on flavored e-cigarettes as the vaping-related deaths intensified.U.S. lawmakers are seizing on the outbreak to scrutinize the e-cigarette industry. A House panel that is investigating the market leader Juul pressed a top CDC official on Tuesday for answers on what’s making people sick. The FDA has also come under fire from lawmakers and public health groups for dropping the ball in regulating the vaping industry.JuulAn employee picks up a Juul Labs device kit for a customer at a store in San Francisco, California, on Wednesday, June 26, 2019.David Paul Morris | Bloomberg | Getty ImagesThe nation’s leading e-cigarette maker, Juul, has come under pressure over the last year for allegedly marketing to underaged kids. But it’s now getting caught up in the public health crisis, even though federal officials say illegal or counterfeit products are likely to blame. Doctors still can’t rule anything out, they say.Juul replaced its CEO Kevin Burns with former Altria executive K.C. Crosthwaite on Wednesday, the day after confirming it was going to reduce its staff and slow hiring.Federal prosecutors in California have also reportedly opened a criminal probe of Juul.Congressional hearingsLawmakers grilled the CDC, and then the FDA, over two days of hearings this week looking into the vaping crisis.CDC Principal Deputy Director Anne Schuchat told Congress the outbreak reinforces the need to curb teen vaping. Preliminary federal survey data shows more than one-quarter of high school students say they use e-cigarettes.She also said doctors worry the nicotine salts used by Juul make its e-cigarettes especially dangerous for teens. Doctors believe they could cross the blood-brain barrier and cause difficulty in learning, memory and attention, as well as priming the body to become addicted to other substances, she said.She added that the CDC is particularly worried about flavored e-cigarettes, “and the role that they play in hooking young people to a life of nicotine, and we really want to avoid another generation being addicted to nicotine so addressing flavors directly is a good idea.”Frank Pallone Jr., D-N.J., the chairman of the House Energy and Commerce Committee, blamed the spike in teen e-cigarette use and outbreak on a 2017 decision by the Food and Drug Administration to delay its review of those products.”I firmly believe that many aspects of the youth vaping epidemic could have been addressed if the FDA had moved forward with reviewing all e-cigarettes on the market when it first had the chance two years ago” he said.Philip Morris and AltriaTobacco giants Philip Morris International and Altria called off merger talks that would have created a $200 billion global behemoth.According to the Wall Street Journal, Philip Morris’ board became increasingly uncomfortable with the deal amid the shifting U.S. regulatory environment on vaping. Altria, the top investor in Juul, unsuccessfully tried to salvage the talks, the Journal said.The companies, which said in August they would discuss a possible all-stock merger of equals, now say they will focus on jointly launching IQOS, a heated tobacco product, in the United States.—CNBC’s Jasmine Wu and Elijah Shama contributed to this report.