The U.S. government has refined how it is measuring an outbreak of breathing illnesses in people who vape, now counting only cases that are most closely linked to electronic cigarette use. Health officials on Thursday said 380 confirmed cases and probable cases have been reported in 36 states and one U.S. territory.

 

That marks a decrease from the 450 cited last week, when officials were also including "possible" cases.

The Centers for Disease Control and Prevention (CDC) and state officials have been investigating an outbreak that began materializing in the Midwest in July.

Doctors say the illnesses resemble an inhalation injury, with the body apparently reacting to a caustic substance that someone breathed in. Symptoms have included shortness of breath, fatigue, chest pain, diarrhea and vomiting.

Many young and previously healthy adolescents and young adults required machines to help them breathe. Six deaths have been reported, all adults and at least some with pre-existing lung problems or other conditions that may have made them more susceptible.

The illnesses are seen as a new phenomenon, and it's taken weeks for CDC officials to come up with a case definition and for states to start following it. Thursday's tally from the CDC was the first based on the new case definition, which counts only breathing illnesses with abnormal chest X-rays, a recent history of vaping, and lab work done to rule out infectious diseases or other possible causes.

No single device, liquid or ingredient has been identified as the cause, and health officials are advising people not to vape at all until more is known.

The states reporting vaping-related lung illnesses to the CDC are Arkansas, California, Colorado, Connecticut, Delaware, Florida, Georgia, Hawaii, Idaho, Iowa, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Michigan, Minnesota, North Carolina, North Dakota, Nebraska, New Jersey, New Mexico, Nevada, New York, Ohio, Oregon, South Carolina, South Dakota, Tennessee, Texas, Utah, Virginia, Washington, Wisconsin and West Virginia — plus the U.S. Virgin Islands.

Some other states have announced they are investigating possible vaping illnesses, but have not yet told CDC that those illnesses met case definitions for confirmed or probable cases, CDC officials said.

The deaths, previously reported, were in California, Illinois, Indiana, Kansas, Minnesota and Oregon.